diff --git a/gulpfile.js b/gulpfile.js
index 1f73af85..5dea5e70 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -11,6 +11,7 @@ var gulp        = require('gulp'),
     zip         = require('gulp-zip'),
     replace     = require('gulp-batch-replace'),
     notify      = require('gulp-notify'),
+    merge       = require('merge2'),
     runSequence = require('run-sequence');
 
 var version  = require('./package.json').version;
@@ -30,10 +31,13 @@ var vendorScripts = [
     'es6-promise/dist/es6-promise.auto.min.js',
     'sweetalert2/dist/sweetalert2.min.js',
     'jqPaginator/dist/1.2.0/jqPaginator.min.js',
-    'regenerator-runtime/runtime.js',
     'resources/assets/dist/js/common.js',
 ];
 
+var vendorScriptsToBeMinified = [
+    'regenerator-runtime/runtime.js',
+];
+
 var vendorStyles = [
     'bootstrap/dist/css/bootstrap.min.css',
     'admin-lte/dist/css/AdminLTE.min.css',
@@ -95,9 +99,12 @@ gulp.task('lint', () => {
 // Concentrate all vendor scripts & styles to one dist file
 gulp.task('publish-vendor', ['compile-es6'], callback => {
     // JavaScript files
-    gulp.src(convertNpmRelativePath(vendorScripts))
+    var js = gulp.src(convertNpmRelativePath(vendorScripts))
+        .pipe(replace(scriptReplacements));
+    var jsToBeMinified = gulp.src(convertNpmRelativePath(vendorScriptsToBeMinified))
+        .pipe(uglify());
+    merge(js, jsToBeMinified)
         .pipe(concat('app.js'))
-        .pipe(replace(scriptReplacements))
         .pipe(gulp.dest(`${distPath}/js/`));
     // CSS files
     gulp.src(convertNpmRelativePath(vendorStyles))
@@ -164,6 +171,7 @@ gulp.task('zip', () => {
             '!node_modules/**/*.*',
             '!storage/textures/**/*.*',
             '!.env',
+            '!.babelrc',
             '!.bowerrc',
             '!.gitignore',
             '!.git/**/*.*',
@@ -201,7 +209,7 @@ gulp.task('watch', () => {
     // watch .scss files
     gulp.watch(`${srcPath}/sass/*.scss`, ['compile-sass'], () => notify('Sass files compiled!'));
     // watch .js files
-    gulp.watch(`${srcPath}/js/*.js`, ['compile-es6'], () => notify('ES6 scripts compiled!'));
+    gulp.watch(`${srcPath}/js/**/*.js`, ['compile-es6'], () => notify('ES6 scripts compiled!'));
     gulp.watch(`${srcPath}/js/general.js`, ['publish-vendor']);
 });
 
diff --git a/package.json b/package.json
index 0ad214b1..91958f62 100644
--- a/package.json
+++ b/package.json
@@ -34,6 +34,7 @@
     "gulp-uglify": "^3.0.0",
     "gulp-zip": "^4.0.0",
     "jest": "^20.0.4",
+    "merge2": "^1.2.0",
     "node-sass": "^4.5.3",
     "run-sequence": "^2.0.0"
   },
diff --git a/resources/assets/src/js/__tests__/admin.test.js b/resources/assets/src/js/__tests__/admin.test.js
index e0cdcea1..d89c31a7 100644
--- a/resources/assets/src/js/__tests__/admin.test.js
+++ b/resources/assets/src/js/__tests__/admin.test.js
@@ -3,6 +3,8 @@
 const $ = require('jquery');
 window.$ = window.jQuery = $;
 
+jest.useFakeTimers();
+
 describe('tests for "customize" module', () => {
   const modulePath = '../admin/customize';
 
@@ -26,7 +28,8 @@ describe('tests for "customize" module', () => {
   it('submit information of skin', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject(new Error));
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
@@ -53,16 +56,33 @@ describe('tests for "customize" module', () => {
 
     await submitColor();
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await submitColor();
+    expect(window.showAjaxError).toBeCalled();
   });
 });
 
 describe('tests for "players" module', () => {
   const modulePath = '../admin/players';
 
-  it('change player reference', async () => {
+  it('show "change player texture" modal dialog', () => {
+    const trans = jest.fn(key => key);
+    const showModal = jest.fn();
+    window.trans = trans;
+    window.showModal = showModal;
+
+    const changeTexture = require(modulePath).changeTexture;
+    changeTexture(1, 'name');
+    const args = showModal.mock.calls[0];
+    expect(args.includes('admin.changePlayerTexture')).toBe(true);
+    expect(args.includes('default')).toBe(true);
+  });
+
+  it('change player preference', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject(new Error));
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
@@ -98,23 +118,28 @@ describe('tests for "players" module', () => {
 
     await $('select').trigger('change');
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await $('select').trigger('change');
+    expect(window.showAjaxError).toBeCalled();
   });
 
   it('submit changed texture information', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const modal = jest.fn();
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.$.fn.modal = modal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <div class="modal" style="display: none" id="shouldBeRemoved"></div>
@@ -141,27 +166,35 @@ describe('tests for "players" module', () => {
 
     await ajaxChangeTexture(1);
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await ajaxChangeTexture(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change player name', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const trans = jest.fn(key => key);
-    const swal = jest.fn(options => {
-      options.inputValidator('newName');
-      return Promise.resolve('newName');
-    });
+    const swal = jest.fn()
+      .mockImplementationOnce(() => Promise.reject())
+      .mockImplementationOnce(options => {
+        options.inputValidator('newName');
+        return Promise.resolve('newName');
+      });
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <table>
@@ -177,6 +210,9 @@ describe('tests for "players" module', () => {
     `;
     const changePlayerName = require(modulePath).changePlayerName;
 
+    await changePlayerName(1, 'oldName');
+    expect(fetch).not.toBeCalled();
+
     await changePlayerName(1, 'oldName');
     expect(swal).toBeCalledWith(expect.objectContaining({
       text: 'admin.changePlayerNameNotice',
@@ -189,16 +225,22 @@ describe('tests for "players" module', () => {
       dataType: 'json',
       data: { pid: 1, name: 'newName' }
     });
-    await changePlayerName(1, 'oldName');
     expect($('tr#1 > td:nth-child(3)').text()).toBe('newName');
     expect(toastr.warning).not.toBeCalled();
     expect(toastr.success).toBeCalledWith('success');
+
+    await changePlayerName(1, 'oldName');
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await changePlayerName(1, 'oldName');
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change owner', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject(new Error));
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
@@ -207,13 +249,14 @@ describe('tests for "players" module', () => {
     const trans = jest.fn(key => key);
     const swal = jest.fn().mockReturnValue(Promise.resolve(2));
     const debounce = jest.fn(fn => fn);
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
     window.swal = swal;
     window.debounce = debounce;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <table>
@@ -248,28 +291,38 @@ describe('tests for "players" module', () => {
       data: { pid: 1, uid: 2 }
     });
     await changeOwner(1, 'oldName');
-    expect($('tr#1 > td:nth-child(2)').text()).toBe((2).toString());
+    expect($('tr#1 > td:nth-child(2)').text()).toBe('2');
     expect(toastr.warning).not.toBeCalled();
     expect(toastr.success).toBeCalledWith('success');
+
+    await changeOwner(1, 'oldName');
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await changeOwner(1, 'oldName');
+    expect(showAjaxError).toBeCalled();
   });
 
   it('delete player', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const trans = jest.fn(key => key);
-    const swal = jest.fn().mockReturnValue(Promise.resolve('newName'));
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <table>
@@ -282,6 +335,9 @@ describe('tests for "players" module', () => {
     `;
     const deletePlayer = require(modulePath).deletePlayer;
 
+    await deletePlayer(1);
+    expect(fetch).not.toBeCalled();
+
     await deletePlayer(1);
     expect(swal).toBeCalledWith({
       text: 'admin.deletePlayerNotice',
@@ -294,10 +350,15 @@ describe('tests for "players" module', () => {
       dataType: 'json',
       data: { pid: 1 }
     });
-    await deletePlayer(1);
     expect(document.getElementById('1')).toBeNull();
     expect(toastr.warning).not.toBeCalled();
     expect(toastr.success).toBeCalledWith('success');
+
+    await deletePlayer(1);
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await deletePlayer(1);
+    expect(showAjaxError).toBeCalled();
   });
 });
 
@@ -307,17 +368,19 @@ describe('tests for "plugins" module', () => {
   it('enable a plugin', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const reloadTable = jest.fn();
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
     $.pluginsTable = {
       ajax: {
         reload: reloadTable
@@ -338,22 +401,27 @@ describe('tests for "plugins" module', () => {
 
     await enablePlugin('plugin');
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await enablePlugin('plugin');
+    expect(showAjaxError).toBeCalled();
   });
 
   it('disable a plugin', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const reloadTable = jest.fn();
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
     $.pluginsTable = {
       ajax: {
         reload: reloadTable
@@ -374,22 +442,30 @@ describe('tests for "plugins" module', () => {
 
     await disablePlugin('plugin');
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await disablePlugin('plugin');
+    expect(showAjaxError).toBeCalled();
   });
 
   it('delete a plugin', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const reloadTable = jest.fn();
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
     $.pluginsTable = {
       ajax: {
         reload: reloadTable
@@ -399,6 +475,9 @@ describe('tests for "plugins" module', () => {
 
     const deletePlugin = require(modulePath).deletePlugin;
 
+    await deletePlugin('plugin');
+    expect(fetch).not.toBeCalled();
+
     await deletePlugin('plugin');
     expect(swal).toBeCalledWith({
       text: 'admin.confirmDeletion',
@@ -410,10 +489,15 @@ describe('tests for "plugins" module', () => {
       url: 'admin/plugins/manage?action=delete&name=plugin',
       dataType: 'json'
     });
-    await deletePlugin('plugin');
     expect(toastr.warning).not.toBeCalled();
     expect(toastr.success).toBeCalledWith('success');
     expect(reloadTable).toBeCalledWith(null, false);
+
+    await deletePlugin('plugin');
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await deletePlugin('plugin');
+    expect(showAjaxError).toBeCalled();
   });
 });
 
@@ -502,23 +586,28 @@ describe('tests for "users" module', () => {
 
   it('change user email', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const trans = jest.fn(key => key);
-    const swal = jest.fn(options => {
-      options.inputValidator('a@b.c');
-      return Promise.resolve('a@b.c');
-    });
+    const swal = jest.fn()
+      .mockImplementationOnce(() => Promise.reject())
+      .mockImplementationOnce(options => {
+        options.inputValidator('a@b.c');
+        return Promise.resolve('a@b.c');
+      });
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <table>
@@ -532,6 +621,9 @@ describe('tests for "users" module', () => {
     `;
     const changeUserEmail = require(modulePath).changeUserEmail;
 
+    await changeUserEmail(1);
+    expect(fetch).not.toBeCalled();
+
     await changeUserEmail(1);
     expect(swal).toBeCalledWith(expect.objectContaining({
       text: 'admin.newUserEmail',
@@ -545,30 +637,40 @@ describe('tests for "users" module', () => {
       dataType: 'json',
       data: { uid: 1, email: 'a@b.c' }
     });
-    await changeUserEmail(1);
     expect($('tr > td:nth-child(2)').text()).toBe('a@b.c');
     expect(toastr.success).toBeCalledWith('success');
+
+    await changeUserEmail(1);
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await changeUserEmail(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change user nick name', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const trans = jest.fn(key => key);
-    const swal = jest.fn(options => {
-      options.inputValidator('foo');
-      return Promise.resolve('foo');
-    });
+    const swal = jest.fn()
+      .mockImplementationOnce(() => Promise.reject())
+      .mockImplementationOnce(options => {
+        options.inputValidator('foo');
+        return Promise.resolve('foo');
+      });
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <table>
@@ -583,6 +685,9 @@ describe('tests for "users" module', () => {
     `;
     const changeUserNickName = require(modulePath).changeUserNickName;
 
+    await changeUserNickName(1);
+    expect(fetch).not.toBeCalled();
+
     await changeUserNickName(1);
     expect(swal).toBeCalledWith(expect.objectContaining({
       text: 'admin.newUserNickname',
@@ -596,30 +701,43 @@ describe('tests for "users" module', () => {
       dataType: 'json',
       data: { uid: 1, nickname: 'foo' }
     });
-    await changeUserNickName(1);
     expect($('tr > td:nth-child(3)').text()).toBe('foo');
     expect(toastr.success).toBeCalledWith('success');
+
+    await changeUserNickName(1);
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await changeUserNickName(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change user password', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const trans = jest.fn(key => key);
-    const swal = jest.fn().mockReturnValue(Promise.resolve('secret'));
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve('secret'));
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     const changeUserPwd = require(modulePath).changeUserPwd;
 
+    await changeUserPwd(1);
+    expect(fetch).not.toBeCalled();
+
     await changeUserPwd(1);
     expect(swal).toBeCalledWith(expect.objectContaining({
       text: 'admin.newUserPassword',
@@ -632,23 +750,30 @@ describe('tests for "users" module', () => {
       dataType: 'json',
       data: { uid: 1, password: 'secret' }
     });
-    await changeUserPwd(1);
     expect(toastr.success).toBeCalledWith('success');
+
+    await changeUserPwd(1);
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await changeUserPwd(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change user score', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <table>
@@ -675,6 +800,9 @@ describe('tests for "users" module', () => {
 
     await changeUserScore('user-1', 50);
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await changeUserScore('user-1', 50);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change ban status', async () => {
@@ -689,18 +817,20 @@ describe('tests for "users" module', () => {
         msg: 'success',
         permission: -1
       }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const trans = jest.fn(key => key);
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <table>
@@ -748,6 +878,9 @@ describe('tests for "users" module', () => {
 
     await require(modulePath).changeBanStatus(1);
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await require(modulePath).changeBanStatus(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change admin status', async () => {
@@ -762,18 +895,20 @@ describe('tests for "users" module', () => {
         msg: 'success',
         permission: 1
       }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const trans = jest.fn(key => key);
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <table>
@@ -821,28 +956,39 @@ describe('tests for "users" module', () => {
 
     await require(modulePath).changeAdminStatus(1);
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await require(modulePath).changeAdminStatus(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('delete a user', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
     const trans = jest.fn(key => key);
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = '<tr id="user-1"></tr>';
     const deleteUserAccount = require(modulePath).deleteUserAccount;
 
+    await deleteUserAccount(1);
+    expect(fetch).not.toBeCalled();
+
     await deleteUserAccount(1);
     expect(swal).toBeCalledWith({
       text: 'admin.deleteUserNotice',
@@ -855,8 +1001,13 @@ describe('tests for "users" module', () => {
       dataType: 'json',
       data: { uid: 1 }
     });
-    await deleteUserAccount(1);
     expect(document.getElementById('user-1')).toBeNull();
+
+    await deleteUserAccount(1);
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await deleteUserAccount(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('"input" element should be focused out when press enter key', () => {
diff --git a/resources/assets/src/js/__tests__/auth.test.js b/resources/assets/src/js/__tests__/auth.test.js
index a479efc3..7105b676 100644
--- a/resources/assets/src/js/__tests__/auth.test.js
+++ b/resources/assets/src/js/__tests__/auth.test.js
@@ -40,17 +40,20 @@ describe('tests for "login" module', () => {
       ))
       .mockImplementationOnce(() => Promise.resolve(
         { errno: 1, msg: 'warning2', login_fails: 4 }
-      ));
+      ))
+      .mockImplementationOnce(() => Promise.reject());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
     const swal = jest.fn();
     const refreshCaptcha = jest.fn();
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.trans = trans;
     window.url = url;
     window.swal = swal;
     window.showMsg = jest.fn();
     window.refreshCaptcha = refreshCaptcha;
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <input id="identification" />
@@ -108,6 +111,9 @@ describe('tests for "login" module', () => {
     expect(swal).toBeCalledWith({ type: 'error', html: 'auth.tooManyFails' });
     expect($('#captcha-form').css('display')).not.toBe('none');
     expect(showMsg).toBeCalledWith('warning2', 'warning');
+
+    await $('button').click();
+    expect(showAjaxError).toBeCalled();
   });
 });
 
@@ -126,18 +132,21 @@ describe('tests for "register" module', () => {
       })
       .mockImplementationOnce(() => Promise.resolve(
         { errno: 1, msg: 'warning' }
-      ));
+      ))
+      .mockImplementationOnce(() => Promise.reject(new Error));
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
     const swal = jest.fn().mockImplementation(() => Promise.resolve());
     const showMsg = jest.fn();
     const refreshCaptcha = jest.fn();
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.trans = trans;
     window.url = url;
     window.swal = swal;
     window.showMsg = showMsg;
     window.refreshCaptcha = refreshCaptcha;
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <input id="email" />
@@ -232,6 +241,9 @@ describe('tests for "register" module', () => {
     expect(refreshCaptcha).toBeCalled();
     expect(showMsg).toBeCalledWith('warning', 'warning');
     expect($('button').html()).toBe('auth.register');
+
+    await $('button').click();
+    expect(showAjaxError).toBeCalled();
   });
 });
 
@@ -246,18 +258,21 @@ describe('tests for "forgot" module', () => {
       })
       .mockImplementationOnce(() => Promise.resolve(
         { errno: 1, msg: 'warning' }
-      ));
+      ))
+      .mockImplementationOnce(() => Promise.reject(new Error));
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
     const swal = jest.fn();
     const showMsg = jest.fn();
     const refreshCaptcha = jest.fn();
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.trans = trans;
     window.url = url;
     window.swal = swal;
     window.showMsg = showMsg;
     window.refreshCaptcha = refreshCaptcha;
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <input id="email" />
@@ -302,6 +317,11 @@ describe('tests for "forgot" module', () => {
     expect(refreshCaptcha).toBeCalled();
     expect(showMsg).toBeCalledWith('warning', 'warning');
     expect($('button').html()).toBe('auth.send');
+
+    await $('button').click();
+    expect($('button').html()).toBe('auth.send');
+    expect($('button').prop('disabled')).toBe(false);
+    expect(showAjaxError).toBeCalled();
   });
 });
 
@@ -316,12 +336,14 @@ describe('tests for "reset" module', () => {
       })
       .mockImplementationOnce(() => Promise.resolve(
         { errno: 1, msg: 'warning' }
-      ));
+      ))
+      .mockImplementationOnce(() => Promise.reject(new Error));
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
     const swal = jest.fn().mockReturnValue(Promise.resolve());
     const showMsg = jest.fn();
     const getQueryString = jest.fn().mockReturnValue('token');
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.trans = trans;
     window.url = url;
@@ -329,6 +351,7 @@ describe('tests for "reset" module', () => {
     window.showMsg = showMsg;
     window.refreshCaptcha = jest.fn();
     window.getQueryString = getQueryString;
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <input id="uid" value="1" />
@@ -389,5 +412,9 @@ describe('tests for "reset" module', () => {
     await $('button').click();
     expect(showMsg).toBeCalledWith('warning', 'warning');
     expect($('button').html()).toBe('auth.reset');
+
+    await $('button').click();
+    expect($('button').html()).toBe('auth.reset');
+    expect(showAjaxError).toBeCalled();
   });
 });
diff --git a/resources/assets/src/js/__tests__/common.test.js b/resources/assets/src/js/__tests__/common.test.js
index 8df7eba0..c9a93da1 100644
--- a/resources/assets/src/js/__tests__/common.test.js
+++ b/resources/assets/src/js/__tests__/common.test.js
@@ -3,6 +3,43 @@
 const $ = require('jquery');
 window.jQuery = window.$ = $;
 
+describe('tests for "cookie" module', () => {
+  it('operates cookies', () => {
+    const cookies = require('../common/cookie');
+
+    expect(cookies.hasItem('key1')).toBe(false);
+    expect(cookies.getItem('key1')).toBeNull();
+
+    expect(cookies.setItem('key1', 'value1')).toBe(true);
+    expect(document.cookie).toBe('key1=value1');
+    expect(cookies.setItem('key2', 'value2')).toBe(true);
+    expect(document.cookie).toBe('key1=value1; key2=value2');
+    expect(cookies.hasItem('key1')).toBe(true);
+    expect(cookies.getItem('key1')).toBe('value1');
+    expect(cookies.hasItem('key2')).toBe(true);
+    expect(cookies.getItem('key2')).toBe('value2');
+    expect(cookies.keys()).toEqual(['key1', 'key2']);
+
+    expect(cookies.setItem('domain', 'value')).toBe(false);
+
+    expect(cookies.removeItem('key0')).toBe(false);
+    expect(cookies.removeItem('key2')).toBe(true);
+    expect(cookies.hasItem('key2')).toBe(false);
+    expect(document.cookie).toBe('key1=value1');
+    expect(cookies.removeItem('key1')).toBe(true);
+
+    expect(cookies.setItem('key3', 'value3', 50));
+    expect(cookies.getItem('key3')).toBe('value3');
+    expect(cookies.setItem('key3', 'value3', Infinity));
+    expect(cookies.getItem('key3')).toBe('value3');
+    expect(cookies.setItem('key3', 'value3', '60'));
+    expect(cookies.getItem('key3')).toBe('value3');
+    expect(cookies.setItem('key4', 'value3', new Date));
+    expect(cookies.removeItem('key3')).toBe(true);
+    expect(document.cookie).toBe('');
+  });
+});
+
 describe('tests for "i18n" module', () => {
   const modulePath = '../common/i18n';
 
@@ -21,6 +58,11 @@ describe('tests for "i18n" module', () => {
   it('get translated text', () => {
     const trans = require(modulePath).trans;
 
+    $.currentLocale = undefined;  // Should load locale automatically
+    $.locales = {
+      en: { text: 'text', nested: { sth: ':sth here!' } }
+    };
+
     expect(trans('text')).toBe('text');
     expect(trans('text.nothing')).toBe('text.nothing');
     expect(trans('nested.sth')).toBe(':sth here!');
@@ -28,22 +70,32 @@ describe('tests for "i18n" module', () => {
   });
 });
 
+jest.useFakeTimers();
+
 describe('tests for "logout" module', () => {
   const modulePath = '../common/logout';
 
   it('logout', async () => {
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
     const trans = jest.fn(key => key);
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ msg: 'success' }))
+      .mockReturnValueOnce(Promise.reject());
+    const showAjaxError = jest.fn();
     window.swal = swal;
     window.trans = trans;
     window.fetch = fetch;
     window.url = jest.fn(path => path);
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = '<button id="logout-button"></button>';
     require(modulePath);
 
+    await $('button').click();
+    expect(fetch).not.toBeCalled();
+
     await $('button').click();
     expect(swal).toBeCalledWith({
       text: 'general.confirmLogout',
@@ -57,11 +109,19 @@ describe('tests for "logout" module', () => {
       url: 'auth/logout',
       dataType: 'json'
     });
+    jest.runAllTimers();
+    expect(url).toBeCalled();
+
     await $('button').click();
     expect(swal).toBeCalledWith({ type: 'success', html: 'success' });
+
+    await $('button').click();
+    expect(showAjaxError).toBeCalled();
   });
 });
 
+jest.useRealTimers();
+
 describe('tests for "notify" module', () => {
   const modulePath = '../common/notify';
 
@@ -87,6 +147,7 @@ describe('tests for "notify" module', () => {
     const warn = jest.fn();
     window.console.warn = warn;
     window.trans = jest.fn(key => key);
+    $.fn.modal = jest.fn();
 
     const showAjaxError = require(modulePath).showAjaxError;
 
@@ -95,6 +156,9 @@ describe('tests for "notify" module', () => {
 
     showAjaxError({});
     expect(warn).toBeCalledWith('Empty Ajax response body.');
+
+    showAjaxError({ responseText: 'error' });
+    expect(window.trans).toBeCalledWith('general.fatalError');
   });
 
   it('show modal dialog', () => {
@@ -146,6 +210,9 @@ describe('tests for "utils" module', () => {
     expect(isEmpty('')).toBe(true);
     expect(isEmpty({})).toBe(true);
     expect(isEmpty({ sth: '' })).toBe(false);
+    expect(isEmpty([])).toBe(true);
+    expect(isEmpty([1])).toBe(false);
+    expect(isEmpty('something')).toBe(false);
   });
 
   it('fake fetch', () => {
@@ -159,7 +226,8 @@ describe('tests for "utils" module', () => {
 
   it('make a debounced function', done => {
     const func = jest.fn();
-    const debounced = require(modulePath).debounce(func, 100);
+    const debounce = require(modulePath).debounce;
+    const debounced = debounce(func, 100);
 
     debounced();
     debounced();
@@ -168,6 +236,9 @@ describe('tests for "utils" module', () => {
       expect(func.mock.calls.length).toBe(1);
       done();
     }, 100);
+
+    expect(() => debounce(func, 'string')).toThrow();
+    expect(() => debounce('not a function', 100)).toThrow();
   });
 
   it('get a absolute url', () => {
diff --git a/resources/assets/src/js/__tests__/skinlib.test.js b/resources/assets/src/js/__tests__/skinlib.test.js
index f8905697..bd349636 100644
--- a/resources/assets/src/js/__tests__/skinlib.test.js
+++ b/resources/assets/src/js/__tests__/skinlib.test.js
@@ -157,13 +157,14 @@ describe('tests for "index" module', () => {
   });
 
   it('reload skin library', async () => {
-    const fetch = jest.fn().mockReturnValue(Promise.resolve({
+    const fetch = jest.fn().mockReturnValueOnce(Promise.resolve({
       items: []
-    }));
+    })).mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
     document.body.innerHTML = `
       <div id="skinlib-paginator"></div>
     `;
@@ -241,7 +242,8 @@ describe('tests for "operations" module', () => {
   it('add to closet (by ajax)', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     window.fetch = fetch;
     const url = jest.fn(path => path);
     window.url = url;
@@ -255,6 +257,8 @@ describe('tests for "operations" module', () => {
       warning: jest.fn()
     };
     window.toastr = toastr;
+    const showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
     $.fn.modal = modal;
 
     document.body.innerHTML = `
@@ -277,17 +281,24 @@ describe('tests for "operations" module', () => {
 
     await ajaxAddToCloset(1, 'name');
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await ajaxAddToCloset(1, 'name');
+    expect(showAjaxError).toBeCalled();
   });
 
   it('remove from closet', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     window.fetch = fetch;
     const url = jest.fn(path => path);
     window.url = url;
     const trans = jest.fn(key => key);
     window.trans = trans;
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
     window.swal = swal;
     const modal = jest.fn();
     const toastr = {
@@ -295,9 +306,14 @@ describe('tests for "operations" module', () => {
       warning: jest.fn()
     };
     window.toastr = toastr;
+    const showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     const removeFromCloset = require(modulePath).removeFromCloset;
 
+    await removeFromCloset(1);
+    expect(fetch).not.toBeCalled();
+
     await removeFromCloset(1);
     expect(swal).toBeCalledWith({
       text: 'user.removeFromClosetNotice',
@@ -312,22 +328,31 @@ describe('tests for "operations" module', () => {
       dataType: 'json',
       data: { tid: 1 }
     });
-    await removeFromCloset(1);
     expect(swal).toBeCalledWith({ type: 'success', html: 'success' });
+
+    await removeFromCloset(1);
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await removeFromCloset(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change texture name', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     window.fetch = fetch;
     const url = jest.fn(path => path);
     window.url = url;
     const trans = jest.fn(key => key);
     window.trans = trans;
-    const swal = jest.fn(option => {
-      option.inputValidator('new-name');
-      return Promise.resolve('new-name');
-    });
+    const swal = jest.fn()
+      .mockImplementationOnce(() => Promise.reject())
+      .mockImplementationOnce(option => {
+        option.inputValidator('new-name');
+        return Promise.resolve('new-name');
+      });
     window.swal = swal;
     const modal = jest.fn();
     const toastr = {
@@ -335,10 +360,15 @@ describe('tests for "operations" module', () => {
       warning: jest.fn()
     };
     window.toastr = toastr;
+    const showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = '<div id="name"></div>';
     const changeTextureName = require(modulePath).changeTextureName;
 
+    await changeTextureName(1, 'oldName');
+    expect(fetch).not.toBeCalled();
+
     await changeTextureName(1, 'oldName');
     expect(swal).toBeCalledWith(expect.objectContaining({
       text: 'skinlib.setNewTextureName',
@@ -352,9 +382,14 @@ describe('tests for "operations" module', () => {
       dataType: 'json',
       data: { tid: 1, new_name: 'new-name' }
     });
-    await changeTextureName(1, 'oldName');
     expect($('div').text()).toBe('new-name');
     expect(toastr.success).toBeCalledWith('success');
+
+    await changeTextureName(1, 'oldName');
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await changeTextureName(1, 'oldName');
+    expect(showAjaxError).toBeCalled();
   });
 
   it('update texture status', () => {
@@ -416,7 +451,8 @@ describe('tests for "operations" module', () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success', public: '0' }))
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     window.fetch = fetch;
     const url = jest.fn(path => path);
     window.url = url;
@@ -430,6 +466,8 @@ describe('tests for "operations" module', () => {
       warning: jest.fn()
     };
     window.toastr = toastr;
+    const showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <a id="1">skinlib.setAsPrivate</a>
@@ -453,17 +491,24 @@ describe('tests for "operations" module', () => {
 
     await changePrivacy(1);
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await changePrivacy(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('delete texture', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     window.fetch = fetch;
     const url = jest.fn(path => path);
     window.url = url;
     const trans = jest.fn(key => key);
     window.trans = trans;
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
     window.swal = swal;
     const modal = jest.fn();
     const toastr = {
@@ -471,9 +516,14 @@ describe('tests for "operations" module', () => {
       warning: jest.fn()
     };
     window.toastr = toastr;
+    const showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     const deleteTexture = require(modulePath).deleteTexture;
 
+    await deleteTexture(1);
+    expect(fetch).not.toBeCalled();
+
     await deleteTexture(1);
     expect(swal).toBeCalledWith({
       text: 'skinlib.deleteNotice',
@@ -486,7 +536,13 @@ describe('tests for "operations" module', () => {
       dataType: 'json',
       data: { tid: 1 }
     });
-    await deleteTexture(1);
     expect(swal).toBeCalledWith({ type: 'success', html: 'success' });
+    expect(url).toBeCalledWith('skinlib');
+
+    await deleteTexture(1);
+    expect(swal).toBeCalledWith({ type: 'warning', html: 'warning' });
+
+    await deleteTexture(1);
+    expect(showAjaxError).toBeCalled();
   });
 });
diff --git a/resources/assets/src/js/__tests__/user.test.js b/resources/assets/src/js/__tests__/user.test.js
index 5eee068f..c65929f1 100644
--- a/resources/assets/src/js/__tests__/user.test.js
+++ b/resources/assets/src/js/__tests__/user.test.js
@@ -11,18 +11,20 @@ describe('tests for "closet" module', () => {
   it('preview textures', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ type: 'skin', hash: 1 }))
-      .mockReturnValueOnce(Promise.resolve({ type: 'cape', hash: 2 }));
+      .mockReturnValueOnce(Promise.resolve({ type: 'cape', hash: 2 }))
+      .mockReturnValueOnce(Promise.reject());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
     const MSP = {
       changeSkin: jest.fn(),
       changeCape: jest.fn()
     };
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.trans = trans;
     window.url = url;
     window.MSP = MSP;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <div id="textures-indicator"></div>
@@ -54,7 +56,6 @@ describe('tests for "closet" module', () => {
         <div class="item-body"></div>
       </div>
     `;
-    window.selectedTextures = [];
 
     await $('#next > .item-body').click();
     expect(fetch).toBeCalledWith({
@@ -65,6 +66,9 @@ describe('tests for "closet" module', () => {
     expect($('#next').hasClass('item-selected')).toBe(true);
     expect(MSP.changeCape).toBeCalledWith('textures/2');
     expect($('#textures-indicator').text()).toBe('general.skin & general.cape');
+
+    await $('#next > .item-body').click();
+    expect(showAjaxError).toBeCalled();
   });
 
   it('render closet', () => {
@@ -107,14 +111,14 @@ describe('tests for "closet" module', () => {
 
   it('reload closet', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({
+      .mockReturnValueOnce(Promise.resolve({
         items: [],
         category: 'skin',
         total_pages: 1
-      }));
+      }))
+      .mockReturnValueOnce(Promise.reject());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
-    const swal = jest.fn().mockReturnValue(Promise.resolve('name'));
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
@@ -123,12 +127,12 @@ describe('tests for "closet" module', () => {
       changeSkin: jest.fn(),
       changeCape: jest.fn()
     };
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.trans = trans;
     window.url = url;
-    window.swal = swal;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <div id="skin-category">
@@ -157,6 +161,9 @@ describe('tests for "closet" module', () => {
       }
     });
     expect($('#closet-paginator').attr('last-skin-page')).toBe('1');
+
+    await reloadCloset('skin', 1, 'q');
+    expect(showAjaxError).toBeCalled();
   });
 
   it('calculate capacity of closet', () => {
@@ -172,10 +179,17 @@ describe('tests for "closet" module', () => {
 
   it('rename item', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
-    const swal = jest.fn().mockReturnValue(Promise.resolve('name'));
+    const swal = jest.fn()
+      .mockImplementationOnce(() => Promise.reject())
+      .mockImplementationOnce(({ inputValidator }) => {
+        inputValidator('name');
+        return Promise.resolve('name');
+      });
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
@@ -184,12 +198,13 @@ describe('tests for "closet" module', () => {
       changeSkin: jest.fn(),
       changeCape: jest.fn()
     };
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.trans = trans;
     window.url = url;
     window.swal = swal;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <div id="skin-category">
@@ -204,6 +219,9 @@ describe('tests for "closet" module', () => {
     `;
     const renameClosetItem = require(modulePath).renameClosetItem;
 
+    await renameClosetItem(1, 'oldName');
+    expect(fetch).not.toBeCalled();
+
     await renameClosetItem(1, 'oldName');
     expect(swal).toBeCalledWith(expect.objectContaining({
       title: trans('user.renameClosetItem'),
@@ -217,18 +235,26 @@ describe('tests for "closet" module', () => {
       dataType: 'json',
       data: { tid: 1, new_name: 'name' }
     });
-
-    await renameClosetItem(1, 'oldName');
     expect(toastr.success).toBeCalledWith('success');
     expect($('span').html('name'));
+
+    await renameClosetItem(1, 'oldName');
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await renameClosetItem(1, 'oldName');
+    expect(showAjaxError).toBeCalled();
   });
 
   it('remove item from closet', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
@@ -237,12 +263,13 @@ describe('tests for "closet" module', () => {
       changeSkin: jest.fn(),
       changeCape: jest.fn()
     };
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.trans = trans;
     window.url = url;
     window.swal = swal;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <div id="skin-category">
@@ -251,6 +278,9 @@ describe('tests for "closet" module', () => {
     `;
     const removeFromCloset = require(modulePath).removeFromCloset;
 
+    await removeFromCloset(1);
+    expect(fetch).not.toBeCalled();
+
     await removeFromCloset(1);
     expect(swal).toBeCalledWith({
       text: 'user.removeFromClosetNotice',
@@ -263,22 +293,30 @@ describe('tests for "closet" module', () => {
       dataType: 'json',
       data: { tid: 1 }
     });
-
-    await removeFromCloset(1);
     expect(swal).toBeCalledWith({ type: 'success', html: 'success' });
     expect(document.getElementById('shouldBeRemoved')).toBeNull();
     expect(trans).toBeCalledWith('user.emptyClosetMsg', { url: url('skinlib?filter=skin') });
     expect($('#skin-category').html()).toBe(
       '<div class="empty-msg">user.emptyClosetMsg</div>'
     );
+
+    await removeFromCloset(1);
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await removeFromCloset(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('set avatar', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
@@ -287,18 +325,22 @@ describe('tests for "closet" module', () => {
       changeSkin: jest.fn(),
       changeCape: jest.fn()
     };
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.trans = trans;
     window.url = url;
     window.swal = swal;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <img alt="User Image" src="src" />
     `;
     const setAsAvatar = require(modulePath).setAsAvatar;
 
+    await setAsAvatar(1);
+    expect(fetch).not.toBeCalled();
+
     await setAsAvatar(1);
     expect(swal).toBeCalledWith({
       title: 'user.setAvatar',
@@ -312,10 +354,14 @@ describe('tests for "closet" module', () => {
       dataType: 'json',
       data: { tid: 1 }
     });
-
-    await setAsAvatar(1);
     expect(toastr.success).toBeCalledWith('success');
     expect($('img').attr('src').endsWith('src')).toBe(false);
+
+    await setAsAvatar(1);
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await setAsAvatar(1);
+    expect(showAjaxError).toBeCalled();
   });
 });
 
@@ -325,27 +371,32 @@ describe('tests for "player" module', () => {
   it('show player texture preview', async () => {
     const url = jest.fn(path => path);
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({
+      .mockReturnValueOnce(Promise.resolve({
         tid_steve: 1,
         tid_alex: 2,
         tid_cape: 3,
-        preference: 'steve',
+        preference: 'default',
         player_name: 'name'
-      }));
-    window.url = url;
-    window.fetch = fetch;
-    window.showAjaxError = jest.fn();
-    window.TexturePreview = require('../common/texture-preview');
-    window.MSP = {
+      }))
+      .mockReturnValueOnce(Promise.reject());
+    const showAjaxError = jest.fn();
+    const MSP = {
       changeSkin: jest.fn(),
       changeCape: jest.fn(),
       setStatus: jest.fn(),
       getStatus: jest.fn()
     };
+    window.url = url;
+    window.fetch = fetch;
+    window.showAjaxError = showAjaxError;
+    window.TexturePreview = require('../common/texture-preview');
+    window.MSP = MSP;
+    window.defaultSkin = 'steve_base64';
 
     document.body.innerHTML = `
       <div id="1" class="player-selected player"></div>
       <div id="2" class="player"></div>
+      <div id="preview-switch"></div>
     `;
     require(modulePath);
 
@@ -358,21 +409,29 @@ describe('tests for "player" module', () => {
       dataType: 'json',
       data: { pid: '2' }
     });
+
+    await $('#2').click();
+    expect(showAjaxError).toBeCalled();
+
+    $('#preview-switch').click();
+    expect(window.TexturePreview.previewType).toBe('2D');
   });
 
-  it('change player reference', async () => {
+  it('change player preference', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <select id="preference" pid="1">
@@ -397,11 +456,16 @@ describe('tests for "player" module', () => {
 
     await $('select').trigger('change');
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await $('select').trigger('change');
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change player name', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const trans = jest.fn(key => key);
     const toastr = {
@@ -409,17 +473,18 @@ describe('tests for "player" module', () => {
       warning: jest.fn()
     };
     const swal = jest.fn()
+      .mockImplementationOnce(() => Promise.reject())
       .mockImplementationOnce(options => {
         options.inputValidator('name');
         return Promise.resolve('name');
-      })
-      .mockImplementation(() => Promise.resolve());
+      });
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.trans = trans;
     window.toastr = toastr;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <input id="player_name" placeholder="placeholder" />
@@ -432,6 +497,9 @@ describe('tests for "player" module', () => {
     `;
     const changePlayerName = require(modulePath).changePlayerName;
 
+    await changePlayerName(1);
+    expect(fetch).not.toBeCalled();
+
     await changePlayerName(1);
     expect(swal).toBeCalledWith(expect.objectContaining({
       title: 'user.changePlayerName',
@@ -446,27 +514,47 @@ describe('tests for "player" module', () => {
       dataType: 'json',
       data: { pid: 1, new_player_name: 'name' }
     });
-    await changePlayerName(1);
     expect(swal).toBeCalledWith({ type: 'success', html: 'success' });
     expect($('#player-name').html()).toBe('name');
+
+    await changePlayerName(1);
+    expect(swal).toBeCalledWith({ type: 'warning', html: 'warning' });
+
+    await changePlayerName(1);
+    expect(showAjaxError).toBeCalled();
+  });
+
+  it('show "clear texture" modal dialog', () => {
+    const { clearTexture } = require(modulePath);
+    const trans = jest.fn(key => key);
+    const showModal = jest.fn();
+    window.trans = trans;
+    window.showModal = showModal;
+
+    clearTexture();
+    const args = showModal.mock.calls[0];
+    expect(args.includes('user.chooseClearTexture')).toBe(true);
+    expect(args.includes('default')).toBe(true);
   });
 
   it('submit clearing texture request', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const trans = jest.fn(key => key);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
+    const showAjaxError = jest.fn();
     const modal = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.trans = trans;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
     $.fn.modal = modal;
 
     document.body.innerHTML = `
@@ -496,28 +584,39 @@ describe('tests for "player" module', () => {
 
     await ajaxClearTexture(1);
     expect(swal).lastCalledWith({ type: 'error', html: 'warning' });
+
+    await ajaxClearTexture(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('delete player', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn()
     };
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <tr id="1"></tr>
     `;
     const deletePlayer = require(modulePath).deletePlayer;
 
+    await deletePlayer(1);
+    expect(fetch).not.toBeCalled();
+
     await deletePlayer(1);
     expect(swal).toBeCalledWith({
       title: 'user.deletePlayer',
@@ -533,16 +632,21 @@ describe('tests for "player" module', () => {
       dataType: 'json',
       data: { pid: 1 }
     });
-
-    await deletePlayer(1);
     expect(swal).lastCalledWith({ type: 'success', html: 'success' });
     expect(document.getElementById('1')).toBeNull();
+
+    await deletePlayer(1);
+    expect(toastr.warning).toBeCalledWith('warning');
+
+    await deletePlayer(1);
+    expect(showAjaxError).toBeCalled();
   });
 
   it('add a new player', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
@@ -550,11 +654,12 @@ describe('tests for "player" module', () => {
     };
     const swal = jest.fn().mockReturnValue(Promise.resolve());
     const modal = jest.fn();
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
     $.fn.modal = modal;
 
     document.body.innerHTML = `
@@ -570,31 +675,36 @@ describe('tests for "player" module', () => {
       data: { player_name: 'name' }
     });
     expect(swal).toBeCalledWith({ type: 'success', html: 'success' });
+    expect(modal).toBeCalled();
 
     await addNewPlayer();
     expect(toastr.warning).toBeCalledWith('warning');
-    expect(modal.mock.calls.length).toBe(1);
+
+    await addNewPlayer();
+    expect(showAjaxError).toBeCalled();
   });
 
   it('set texture', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const url = jest.fn(path => path);
     const toastr = {
       success: jest.fn(),
       warning: jest.fn(),
       info: jest.fn()
     };
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const swal = jest.fn();
     const modal = jest.fn();
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.url = url;
     window.toastr = toastr;
     window.swal = swal;
     $.fn.modal = modal;
     window.selectedTextures = {};
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <input name="player" id="1" />
@@ -622,6 +732,9 @@ describe('tests for "player" module', () => {
     await setTexture();
     expect(toastr.warning).toBeCalledWith('warning');
     expect(modal.mock.calls.length).toBe(1);
+
+    await setTexture();
+    expect(showAjaxError).toBeCalled();
   });
 });
 
@@ -630,16 +743,22 @@ describe('tests for "profile" module', () => {
 
   it('change nickname', async () => {
     const fetch = jest.fn()
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.resolve())
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValueOnce(Promise.resolve());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.swal = swal;
     window.trans = trans;
     window.url = url;
     window.debounce = jest.fn(fn => fn);
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <div class="nickname"></div>
@@ -649,8 +768,12 @@ describe('tests for "profile" module', () => {
 
     await changeNickName();
     expect(swal).toBeCalledWith({ type: 'error', html: 'user.emptyNewNickName' });
+    expect(fetch).not.toBeCalled();
 
     $('input').val('name');
+    await changeNickName();
+    expect(fetch).not.toBeCalled();
+
     await changeNickName();
     expect(trans).toBeCalledWith('user.changeNickName', { new_nickname: 'name' });
     expect(swal).toBeCalledWith({
@@ -664,17 +787,22 @@ describe('tests for "profile" module', () => {
       dataType: 'json',
       data: { new_nickname: 'name' }
     });
-
-    await changeNickName();
     expect($('.nickname').text()).toBe('name');
     expect(swal).toBeCalledWith({ type: 'success', html: 'success' });
+
+    await changeNickName();
+    expect(swal).toBeCalled();
+
+    await changeNickName();
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change password', async () => {
     const fetch = jest.fn()
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
       .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
-      .mockReturnValue(Promise.resolve({ errno: 0, msg: 'success' }));
+      .mockReturnValueOnce(Promise.reject());
     const swal = jest.fn().mockReturnValue(Promise.resolve());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
@@ -682,13 +810,20 @@ describe('tests for "profile" module', () => {
       info: jest.fn(),
       warning: jest.fn()
     };
+    const showAjaxError = jest.fn();
+    const docCookies = {
+      removeItem: jest.fn()
+    };
     window.fetch = fetch;
     window.swal = swal;
     window.trans = trans;
     window.url = url;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
-    window.logout = jest.fn().mockReturnValue(Promise.resolve({ errno: 0 }));
+    window.showAjaxError = showAjaxError;
+    window.logout = jest.fn()
+      .mockReturnValueOnce(Promise.resolve({ errno: 0 }))
+      .mockReturnValueOnce(Promise.reject());
+    window.docCookies = docCookies;
 
     document.body.innerHTML = `
       <input id="password" />
@@ -725,32 +860,49 @@ describe('tests for "profile" module', () => {
       dataType: 'json',
       data: { current_password: 'password', new_password: 'new-password' }
     });
+    expect(logout).toBeCalled();
+
+    await changePassword();
+    expect(docCookies.removeItem).toBeCalledWith('token');
 
     await changePassword();
     expect(swal).toBeCalledWith({ type: 'warning', text: 'warning' });
 
     await changePassword();
-    expect(logout).toBeCalled();
+    expect(showAjaxError).toBeCalled();
   });
 
   it('change email', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
-    const swal = jest.fn().mockReturnValue(Promise.resolve());
+      .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
+    const swal = jest.fn()
+      .mockReturnValueOnce(Promise.resolve())
+      .mockReturnValueOnce(Promise.resolve())
+      .mockReturnValueOnce(Promise.reject())
+      .mockReturnValue(Promise.resolve());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
     const toastr = {
       info: jest.fn(),
       warning: jest.fn()
     };
+    const showAjaxError = jest.fn();
+    const docCookies = {
+      removeItem: jest.fn()
+    };
     window.fetch = fetch;
     window.swal = swal;
     window.trans = trans;
     window.url = url;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
-    window.logout = jest.fn().mockReturnValue(Promise.resolve({ errno: 0 }));
+    window.showAjaxError = showAjaxError;
+    window.logout = jest.fn()
+      .mockReturnValueOnce(Promise.resolve({ errno: 0 }))
+      .mockReturnValueOnce(Promise.reject());
+    window.docCookies = docCookies;
 
     document.body.innerHTML = `
       <input id="new-email" />
@@ -758,14 +910,17 @@ describe('tests for "profile" module', () => {
     `;
     const changeEmail = require(modulePath).changeEmail;
 
-    changeEmail();
+    await changeEmail();
     expect(swal).toBeCalledWith({ type: 'error', html: 'user.emptyNewEmail' });
+    expect(fetch).not.toBeCalled();
 
     $('#new-email').val('email');
-    changeEmail();
+    await changeEmail();
     expect(swal).toBeCalledWith({ type: 'warning', html: 'auth.invalidEmail' });
 
     $('#new-email').val('a@b.c');
+    await changeEmail();    // Suppose the user cancelled changing email
+
     await changeEmail();
     expect(trans).toBeCalledWith('user.changeEmail', { new_email: 'a@b.c' });
     expect(swal).toBeCalledWith({
@@ -779,12 +934,24 @@ describe('tests for "profile" module', () => {
       dataType: 'json',
       data: { new_email: 'a@b.c', password: 'pwd' }
     });
+    expect(swal).toBeCalledWith({ type: 'success', text: 'success' });
+    expect(logout).toBeCalled();
+
+    await changeEmail();
+    expect(docCookies.removeItem).toBeCalled();
+
+    await changeEmail();
+    expect(swal).toBeCalledWith({ type: 'warning', text: 'warning' });
+
+    await changeEmail();
+    expect(showAjaxError).toBeCalled();
   });
 
   it('delete account', async () => {
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({ errno: 0, msg: 'success' }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     const swal = jest.fn().mockReturnValue(Promise.resolve());
     const trans = jest.fn(key => key);
     const url = jest.fn(path => path);
@@ -792,12 +959,13 @@ describe('tests for "profile" module', () => {
       info: jest.fn(),
       warning: jest.fn()
     };
+    const showAjaxError = jest.fn();
     window.fetch = fetch;
     window.swal = swal;
     window.trans = trans;
     window.url = url;
     window.toastr = toastr;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
 
     document.body.innerHTML = `
       <div class="modal-body">
@@ -806,7 +974,7 @@ describe('tests for "profile" module', () => {
     `;
     const deleteAccount = require(modulePath).deleteAccount;
 
-    deleteAccount();
+    await deleteAccount();
     expect(swal).toBeCalledWith({ type: 'warning', html: 'user.emptyDeletePassword' });
 
     $('#password').val('password');
@@ -818,9 +986,13 @@ describe('tests for "profile" module', () => {
       data: { password: 'password' }
     });
     expect(swal).toBeCalledWith({ type: 'success', html: 'success' });
+    expect(url).toBeCalledWith('auth/login');
 
     await deleteAccount();
     expect(swal).toBeCalledWith({ type: 'warning', html: 'warning' });
+
+    await deleteAccount();
+    expect(showAjaxError).toBeCalled();
   });
 });
 
@@ -835,11 +1007,12 @@ describe('tests for "sign" module', () => {
     };
     const trans = jest.fn(key => key);
     const swal = jest.fn().mockReturnValue(Promise.resolve());
+    const showAjaxError = jest.fn();
     window.url = url;
     window.toastr = toastr;
     window.trans = trans;
     window.swal = swal;
-    window.showAjaxError = jest.fn();
+    window.showAjaxError = showAjaxError;
     window.debounce = fn => fn;
     const fetch = jest.fn()
       .mockReturnValueOnce(Promise.resolve({
@@ -864,7 +1037,8 @@ describe('tests for "sign" module', () => {
           percentage: 50
         }
       }))
-      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }));
+      .mockReturnValueOnce(Promise.resolve({ errno: 1, msg: 'warning' }))
+      .mockReturnValueOnce(Promise.reject());
     window.fetch = fetch;
 
     document.body.innerHTML = `
@@ -903,5 +1077,8 @@ describe('tests for "sign" module', () => {
 
     await sign();
     expect(toastr.warning).toBeCalledWith('warning');
+
+    await sign();
+    expect(showAjaxError).toBeCalled();
   });
 });
diff --git a/resources/assets/src/js/admin/common.js b/resources/assets/src/js/admin/common.js
index df2975b0..cbe87688 100644
--- a/resources/assets/src/js/admin/common.js
+++ b/resources/assets/src/js/admin/common.js
@@ -23,27 +23,30 @@ $(document).ready(() => {
     }
 });
 
-function sendFeedback() {
+async function sendFeedback() {
     if (docCookies.getItem('feedback_sent') !== null)
         return;
 
-    fetch({
-        url: 'https://work.prinzeugen.net/statistics/feedback',
-        type: 'POST',
-        dataType: 'json',
-        data: {
-            site_name: blessing.site_name,
-            site_url: blessing.base_url,
-            version: blessing.version
-        }
-    }).then(({ errno }) => {
+    try {
+        const { errno } = await fetch({
+            url: 'https://work.prinzeugen.net/statistics/feedback',
+            type: 'POST',
+            dataType: 'json',
+            data: {
+                site_name: blessing.site_name,
+                site_url: blessing.base_url,
+                version: blessing.version
+            }
+        });
         if (errno === 0) {
             // Will be expired when current session ends
             docCookies.setItem('feedback_sent', Date.now());
 
             console.log('Feedback sent. Thank you!');
         }
-    });
+    } catch (error) {
+        //
+    }
 }
 
 if (typeof require !== 'undefined' && typeof module !== 'undefined') {
diff --git a/resources/assets/src/js/admin/customize.js b/resources/assets/src/js/admin/customize.js
index f9fc5e90..bbf32d5b 100644
--- a/resources/assets/src/js/admin/customize.js
+++ b/resources/assets/src/js/admin/customize.js
@@ -9,15 +9,18 @@ $('#layout-skins-list [data-skin]').click(function (e) {
     current_skin = skin_name;
 });
 
-function submitColor() {
-    fetch({
-        type: 'POST',
-        url: url('admin/customize?action=color'),
-        dataType: 'json',
-        data: { color_scheme: current_skin }
-    }).then(({ errno, msg }) => {
-        (errno == 0) ? toastr.success(msg) : toastr.warning(msg);
-    }).catch(showAjaxError);
+async function submitColor() {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/customize?action=color'),
+            dataType: 'json',
+            data: { color_scheme: current_skin }
+        });
+        errno == 0 ? toastr.success(msg) : toastr.warning(msg);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 $('#color-submit').click(submitColor);
diff --git a/resources/assets/src/js/admin/players.js b/resources/assets/src/js/admin/players.js
index b9be9f1c..7e42dc74 100644
--- a/resources/assets/src/js/admin/players.js
+++ b/resources/assets/src/js/admin/players.js
@@ -1,17 +1,20 @@
 'use strict';
 
-function changePreference() {
-    fetch({
-        type: 'POST',
-        url: url('admin/players?action=preference'),
-        dataType: 'json',
-        data: {
-            pid: $(this).parent().parent().attr('id'),
-            preference: $(this).val()
-        }
-    }).then(({ errno, msg }) => {
-        (errno == 0) ? toastr.success(msg) : toastr.warning(msg);
-    }).catch(showAjaxError);
+async function changePreference() {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/players?action=preference'),
+            dataType: 'json',
+            data: {
+                pid: $(this).parent().parent().attr('id'),
+                preference: $(this).val()
+            }
+        });
+        errno == 0 ? toastr.success(msg) : toastr.warning(msg);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 function changeTexture(pid, playerName) {
@@ -35,21 +38,22 @@ function changeTexture(pid, playerName) {
     return;
 }
 
-function ajaxChangeTexture(pid) {
+async function ajaxChangeTexture(pid) {
     // Remove interference of modal which is hide
     $('.modal').each(function () {
         if ($(this).css('display') == 'none') $(this).remove();
     });
 
-    var model = $('#model').val();
-    var tid = $('#tid').val();
+    const model = $('#model').val();
+    const tid = $('#tid').val();
 
-    fetch({
-        type: 'POST',
-        url: url('admin/players?action=texture'),
-        dataType: 'json',
-        data: { pid: pid, model: model, tid: tid }
-    }).then(({ errno, msg }) => {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/players?action=texture'),
+            dataType: 'json',
+            data: { pid: pid, model: model, tid: tid }
+        });
         if (errno == 0) {
             $(`#${pid}-${model}`).attr('src', url(`preview/64/${tid}.png`));
             $('.modal').modal('hide');
@@ -58,26 +62,35 @@ function ajaxChangeTexture(pid) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function changePlayerName(pid, oldName) {
+async function changePlayerName(pid, oldName) {
     let dom = $(`tr#${pid} > td:nth-child(3)`);
-    let newPlayerName = '';
+    let newPlayerName;
 
-    swal({
-        text: trans('admin.changePlayerNameNotice'),
-        input: 'text',
-        inputValue: oldName,
-        inputValidator: name => (new Promise((resolve, reject) => {
-            (newPlayerName = name) ? resolve() : reject(trans('admin.emptyPlayerName'));
-        }))
-    }).then(name => fetch({
-        type: 'POST',
-        url: url('admin/players?action=name'),
-        dataType: 'json',
-        data: { pid: pid, name: name }
-    })).then(({ errno, msg }) => {
+    try {
+        newPlayerName = await swal({
+            text: trans('admin.changePlayerNameNotice'),
+            input: 'text',
+            inputValue: oldName,
+            inputValidator: name => (new Promise((resolve, reject) => {
+                name ? resolve() : reject(trans('admin.emptyPlayerName'));
+            }))
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/players?action=name'),
+            dataType: 'json',
+            data: { pid: pid, name: newPlayerName }
+        });
         if (errno == 0) {
             dom.text(newPlayerName);
 
@@ -85,7 +98,9 @@ function changePlayerName(pid, oldName) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    } 
 }
 
 function changeOwner(pid) {
@@ -97,68 +112,81 @@ function changeOwner(pid) {
         input: 'number',
         inputValue: dom.text(),
         showCancelButton: true
-    }).then(uid => {
+    }).then(async uid => {
         owner = uid;
 
-        return fetch({
-            type: 'POST',
-            url: url('admin/players?action=owner'),
-            dataType: 'json',
-            data: { pid: pid, uid: uid }
-        });
-    }).then(({ errno, msg }) => {
-        if (errno == 0) {
-            dom.text(owner);
-            toastr.success(msg);
-        } else {
-            toastr.warning(msg);
+        try {
+            const { errno, msg } = await fetch({
+                type: 'POST',
+                url: url('admin/players?action=owner'),
+                dataType: 'json',
+                data: { pid, uid }
+            });
+            if (errno == 0) {
+                dom.text(owner);
+                toastr.success(msg);
+            } else {
+                toastr.warning(msg);
+            }
+        } catch (error) {
+            showAjaxError(error);
         }
-    }).catch(showAjaxError);
+    });
 
-    $('.swal2-input').on('input', debounce(() => {
+    $('.swal2-input').on('input', debounce(async () => {
         let uid = $('.swal2-input').val();
 
         if (isNaN(uid) || uid <= 0)
             return;
 
-        fetch({
-            type: 'GET',
-            url: url(`admin/user/${uid}`),
-            dataType: 'json'
-        }).then(result => {
+        try {
+            const { user } = await fetch({
+                type: 'GET',
+                url: url(`admin/user/${uid}`),
+                dataType: 'json'
+            });
             $('.swal2-content').html(
                 trans('admin.changePlayerOwner') +
                 '<small style="display: block; margin-top: .5em;">' +
-                trans('admin.targetUser', { nickname: result.user.nickname }) +
+                trans('admin.targetUser', { nickname: user.nickname }) +
                 '</small>'
             );
-        }).catch(() => {
+        } catch (error) {
             $('.swal2-content').html(`
                 ${trans('admin.changePlayerOwner')}<br>
                 <small>${trans('admin.noSuchUser')}</small>
             `);
-        });
+        }
     }, 350));
 }
 
-function deletePlayer(pid) {
-    swal({
-        text: trans('admin.deletePlayerNotice'),
-        type: 'warning',
-        showCancelButton: true
-    }).then(() => fetch({
-        type: 'POST',
-        url: url('admin/players?action=delete'),
-        dataType: 'json',
-        data: { pid: pid }
-    })).then(({ errno, msg }) => {
+async function deletePlayer(pid) {
+    try {
+        await swal({
+            text: trans('admin.deletePlayerNotice'),
+            type: 'warning',
+            showCancelButton: true
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/players?action=delete'),
+            dataType: 'json',
+            data: { pid: pid }
+        });
         if (errno == 0) {
             $(`tr#${pid}`).remove();
             toastr.success(msg);
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 if (typeof require !== 'undefined' && typeof module !== 'undefined') {
diff --git a/resources/assets/src/js/admin/plugins.js b/resources/assets/src/js/admin/plugins.js
index 34574452..822ed534 100644
--- a/resources/assets/src/js/admin/plugins.js
+++ b/resources/assets/src/js/admin/plugins.js
@@ -1,11 +1,12 @@
 'use strict';
 
-function enablePlugin(name) {
-    fetch({
-        type: 'POST',
-        url: url(`admin/plugins/manage?action=enable&name=${name}`),
-        dataType: 'json'
-    }).then(({ errno, msg }) => {
+async function enablePlugin(name) {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url(`admin/plugins/manage?action=enable&name=${name}`),
+            dataType: 'json'
+        });
         if (errno == 0) {
             toastr.success(msg);
 
@@ -13,15 +14,18 @@ function enablePlugin(name) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function disablePlugin(name) {
-    fetch({
-        type: 'POST',
-        url: url(`admin/plugins/manage?action=disable&name=${name}`),
-        dataType: 'json'
-    }).then(({ errno, msg }) => {
+async function disablePlugin(name) {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url(`admin/plugins/manage?action=disable&name=${name}`),
+            dataType: 'json'
+        });
         if (errno == 0) {
             toastr.success(msg);
 
@@ -29,19 +33,28 @@ function disablePlugin(name) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function deletePlugin(name) {
-    swal({
-        text: trans('admin.confirmDeletion'),
-        type: 'warning',
-        showCancelButton: true
-    }).then(() => fetch({
-        type: 'POST',
-        url: url(`admin/plugins/manage?action=delete&name=${name}`),
-        dataType: 'json'
-    })).then(({ errno, msg }) => {
+async function deletePlugin(name) {
+    try {
+        await swal({
+            text: trans('admin.confirmDeletion'),
+            type: 'warning',
+            showCancelButton: true
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url(`admin/plugins/manage?action=delete&name=${name}`),
+            dataType: 'json'
+        });
         if (errno == 0) {
             toastr.success(msg);
 
@@ -49,7 +62,9 @@ function deletePlugin(name) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 if (typeof require !== 'undefined' && typeof module !== 'undefined') {
diff --git a/resources/assets/src/js/admin/update.js b/resources/assets/src/js/admin/update.js
index 6147b82c..31da29d5 100644
--- a/resources/assets/src/js/admin/update.js
+++ b/resources/assets/src/js/admin/update.js
@@ -88,14 +88,17 @@ function downloadUpdates() {
 
 }
 
-function checkForUpdates() {
-    fetch({ url: url('admin/update/check') }).then(data => {
+async function checkForUpdates() {
+    try {
+        const data = await fetch({ url: url('admin/update/check') });
         if (data.available == true) {
             let dom = `<span class="label label-primary pull-right">v${data.latest}</span>`;
 
             $(`[href="${url('admin/update')}"]`).append(dom);
         }
-    });
+    } catch (error) {
+        //
+    }
 }
 
 if (typeof require !== 'undefined' && typeof module !== 'undefined') {
diff --git a/resources/assets/src/js/admin/users.js b/resources/assets/src/js/admin/users.js
index 7b66e3d3..f650e76a 100644
--- a/resources/assets/src/js/admin/users.js
+++ b/resources/assets/src/js/admin/users.js
@@ -1,23 +1,31 @@
 'use strict';
 
-function changeUserEmail(uid) {
+async function changeUserEmail(uid) {
     let dom = $(`tr#user-${uid} > td:nth-child(2)`),
         newUserEmail = '';
 
-    swal({
-        text: trans('admin.newUserEmail'),
-        showCancelButton: true,
-        input: 'text',
-        inputValue: dom.text(),
-        inputValidator: value => (new Promise((resolve, reject) => {
-            (newUserEmail = value) ? resolve() : reject(trans('auth.emptyEmail'));
-        }))
-    }).then(email => fetch({
-        type: 'POST',
-        url: url('admin/users?action=email'),
-        dataType: 'json',
-        data: { uid: uid, email: email }
-    })).then(({ errno, msg }) => {
+    try {
+        newUserEmail = await swal({
+            text: trans('admin.newUserEmail'),
+            showCancelButton: true,
+            input: 'text',
+            inputValue: dom.text(),
+            inputValidator: value => (new Promise((resolve, reject) => {
+                value ? resolve() : reject(trans('auth.emptyEmail'));
+            }))
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/users?action=email'),
+            dataType: 'json',
+            data: { uid: uid, email: newUserEmail }
+        });
+
         if (errno == 0) {
             dom.text(newUserEmail);
 
@@ -25,27 +33,36 @@ function changeUserEmail(uid) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function changeUserNickName(uid) {
+async function changeUserNickName(uid) {
     let dom = $(`tr#user-${uid} > td:nth-child(3)`),
         newNickName = '';
 
-    swal({
-        text: trans('admin.newUserNickname'),
-        showCancelButton: true,
-        input: 'text',
-        inputValue: dom.text(),
-        inputValidator: value => (new Promise((resolve, reject) => {
-            (newNickName = value) ? resolve() : reject(trans('auth.emptyNickname'));
-        }))
-    }).then(nickname => fetch({
-        type: 'POST',
-        url: url('admin/users?action=nickname'),
-        dataType: 'json',
-        data: { uid: uid, nickname: nickname }
-    })).then(({ errno, msg }) => {
+    try {
+        newNickName = await swal({
+            text: trans('admin.newUserNickname'),
+            showCancelButton: true,
+            input: 'text',
+            inputValue: dom.text(),
+            inputValidator: value => (new Promise((resolve, reject) => {
+                value ? resolve() : reject(trans('auth.emptyNickname'));
+            }))
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/users?action=nickname'),
+            dataType: 'json',
+            data: { uid: uid, nickname: newNickName }
+        });
         if (errno == 0) {
             dom.text(newNickName);
 
@@ -53,43 +70,60 @@ function changeUserNickName(uid) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function changeUserPwd(uid) {
-    swal({
-        text: trans('admin.newUserPassword'),
-        showCancelButton: true,
-        input: 'password',
-    }).then(password => fetch({
-        type: 'POST',
-        url: url('admin/users?action=password'),
-        dataType: 'json',
-        data: { uid: uid, password: password }
-    })).then(({ errno, msg }) => {
-        (errno == 0) ? toastr.success(msg) : toastr.warning(msg);
-    }).catch(showAjaxError);
+async function changeUserPwd(uid) {
+    let password;
+    try {
+        password = await swal({
+            text: trans('admin.newUserPassword'),
+            showCancelButton: true,
+            input: 'password',
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/users?action=password'),
+            dataType: 'json',
+            data: { uid: uid, password: password }
+        });
+        errno == 0 ? toastr.success(msg) : toastr.warning(msg);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function changeUserScore(uid, score) {
-    fetch({
-        type: 'POST',
-        url: url('admin/users?action=score'),
-        dataType: 'json',
-        // Handle id formatted as '#user-1234'
-        data: { uid: uid.slice(5), score: score }
-    }).then(({ errno, msg }) => {
-        (errno == 0) ? toastr.success(msg) : toastr.warning(msg);
-    }).catch(showAjaxError);
+async function changeUserScore(uid, score) {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/users?action=score'),
+            dataType: 'json',
+            // Handle id formatted as '#user-1234'
+            data: { uid: uid.slice(5), score: score }
+        });
+        errno == 0 ? toastr.success(msg) : toastr.warning(msg);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function changeBanStatus(uid) {
-    fetch({
-        type: 'POST',
-        url: url('admin/users?action=ban'),
-        dataType: 'json',
-        data: { uid: uid }
-    }).then(({ errno, msg, permission }) => {
+async function changeBanStatus(uid) {
+    try {
+        const { errno, msg, permission } = await fetch({
+            type: 'POST',
+            url: url('admin/users?action=ban'),
+            dataType: 'json',
+            data: { uid: uid }
+        });
+
         if (errno == 0) {
             let dom = $(`#ban-${uid}`);
 
@@ -107,16 +141,20 @@ function changeBanStatus(uid) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function changeAdminStatus(uid) {
-    fetch({
-        type: 'POST',
-        url: url('admin/users?action=admin'),
-        dataType: 'json',
-        data: { uid: uid }
-    }).then(({ errno, msg, permission }) => {
+async function changeAdminStatus(uid) {
+    try {
+        const { errno, msg, permission } = await fetch({
+            type: 'POST',
+            url: url('admin/users?action=admin'),
+            dataType: 'json',
+            data: { uid: uid }
+        });
+
         if (errno == 0) {
             let dom = $(`#admin-${uid}`);
 
@@ -134,27 +172,39 @@ function changeAdminStatus(uid) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function deleteUserAccount(uid) {
-    swal({
-        text: trans('admin.deleteUserNotice'),
-        type: 'warning',
-        showCancelButton: true
-    }).then(() => fetch({
-        type: 'POST',
-        url: url('admin/users?action=delete'),
-        dataType: 'json',
-        data: { uid: uid }
-    })).then(({ errno, msg }) => {
+async function deleteUserAccount(uid) {
+    try {
+        await swal({
+            text: trans('admin.deleteUserNotice'),
+            type: 'warning',
+            showCancelButton: true
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('admin/users?action=delete'),
+            dataType: 'json',
+            data: { uid: uid }
+        });
+
         if (errno == 0) {
             $('tr#user-' + uid).remove();
             toastr.success(msg);
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 $('body').on('keypress', '.score', function(event){
diff --git a/resources/assets/src/js/auth/forgot.js b/resources/assets/src/js/auth/forgot.js
index bd9ad0da..b240af0e 100644
--- a/resources/assets/src/js/auth/forgot.js
+++ b/resources/assets/src/js/auth/forgot.js
@@ -22,18 +22,19 @@ $('#forgot-button').click(e => {
         } else {
             callback();
         }
-    })(data, () => {
-        fetch({
-            type: 'POST',
-            url: url('auth/forgot'),
-            dataType: 'json',
-            data: data,
-            beforeSend: () => {
-                $('#forgot-button').html(
-                    '<i class="fa fa-spinner fa-spin"></i> ' + trans('auth.sending')
-                ).prop('disabled', 'disabled');
-            }
-        }).then(({ errno, msg }) => {
+    })(data, async () => {
+        try {
+            const { errno, msg } = await fetch({
+                type: 'POST',
+                url: url('auth/forgot'),
+                dataType: 'json',
+                data: data,
+                beforeSend: () => {
+                    $('#forgot-button').html(
+                        '<i class="fa fa-spinner fa-spin"></i> ' + trans('auth.sending')
+                    ).prop('disabled', 'disabled');
+                }
+            });
             if (errno == 0) {
                 showMsg(msg, 'success');
                 $('#forgot-button').html(trans('auth.send')).prop('disabled', 'disabled');
@@ -42,9 +43,9 @@ $('#forgot-button').click(e => {
                 refreshCaptcha();
                 $('#forgot-button').html(trans('auth.send')).prop('disabled', '');
             }
-        }).catch(err => {
-            showAjaxError(err);
+        } catch (error) {
+            showAjaxError(error);
             $('#forgot-button').html(trans('auth.send')).prop('disabled', '');
-        });
+        }
     });
 });
diff --git a/resources/assets/src/js/auth/login.js b/resources/assets/src/js/auth/login.js
index d37b6504..c402b200 100644
--- a/resources/assets/src/js/auth/login.js
+++ b/resources/assets/src/js/auth/login.js
@@ -2,7 +2,7 @@
 
 'use strict';
 
-$('#login-button').click(e => {
+$('#login-button').click(async e => {
     e.preventDefault();
     
     let data = {
@@ -29,21 +29,22 @@ $('#login-button').click(e => {
             }
         }
 
-        fetch({
-            type: 'POST',
-            url: url('auth/login'),
-            dataType: 'json',
-            data: data,
-            beforeSend: () => {
-                $('#login-button').html(
-                    '<i class="fa fa-spinner fa-spin"></i> ' + trans('auth.loggingIn')
-                ).prop('disabled', 'disabled');
-            }
-        }).then(({ errno, msg, login_fails }) => {
+        try {
+            const { errno, msg, login_fails } = await fetch({
+                type: 'POST',
+                url: url('auth/login'),
+                dataType: 'json',
+                data: data,
+                beforeSend: () => {
+                    $('#login-button').html(
+                        '<i class="fa fa-spinner fa-spin"></i> ' + trans('auth.loggingIn')
+                    ).prop('disabled', 'disabled');
+                }
+            });
             if (errno == 0) {
                 swal({ type: 'success', html: msg });
 
-                window.setTimeout(() => {
+                setTimeout(() => {
                     window.location = url(blessing.redirect_to || 'user');
                 }, 1000);
             } else {
@@ -60,9 +61,9 @@ $('#login-button').click(e => {
                 showMsg(msg, 'warning');
                 $('#login-button').html(trans('auth.login')).prop('disabled', '');
             }
-        }).catch(err => {
-            showAjaxError(err);
+        } catch (error) {
+            showAjaxError(error);
             $('#login-button').html(trans('auth.login')).prop('disabled', '');
-        });
+        }
     }
 });
diff --git a/resources/assets/src/js/auth/register.js b/resources/assets/src/js/auth/register.js
index b87b6d10..ec6463f3 100644
--- a/resources/assets/src/js/auth/register.js
+++ b/resources/assets/src/js/auth/register.js
@@ -43,18 +43,19 @@ $('#register-button').click(e => {
         }
 
         return;
-    })(data, () => {
-        fetch({
-            type: 'POST',
-            url: url('auth/register'),
-            dataType: 'json',
-            data: data,
-            beforeSend: function () {
-                $('#register-button').html(
-                    '<i class="fa fa-spinner fa-spin"></i> ' + trans('auth.registering')
-                ).prop('disabled', 'disabled');
-            }
-        }).then(({ errno, msg, redirect }) => {
+    })(data, async () => {
+        try {
+            const { errno, msg, redirect } = await fetch({
+                type: 'POST',
+                url: url('auth/register'),
+                dataType: 'json',
+                data: data,
+                beforeSend: function () {
+                    $('#register-button').html(
+                        '<i class="fa fa-spinner fa-spin"></i> ' + trans('auth.registering')
+                    ).prop('disabled', 'disabled');
+                }
+            });
             if (errno == 0) {
                 swal({ type: 'success', html: msg })
                     .then(() => window.location = url('user'));
@@ -69,9 +70,9 @@ $('#register-button').click(e => {
                 refreshCaptcha();
                 $('#register-button').html(trans('auth.register')).prop('disabled', '');
             }
-        }).catch(err => {
-            showAjaxError(err);
+        } catch (error) {
+            showAjaxError(error);
             $('#register-button').html(trans('auth.register')).prop('disabled', '');
-        });
+        }
     });
 });
diff --git a/resources/assets/src/js/auth/reset.js b/resources/assets/src/js/auth/reset.js
index f66254d3..28bfe00e 100644
--- a/resources/assets/src/js/auth/reset.js
+++ b/resources/assets/src/js/auth/reset.js
@@ -25,18 +25,19 @@ $('#reset-button').click(e => {
         } else {
             callback();
         }
-    })(data, () => {
-        fetch({
-            type: 'POST',
-            url: url('auth/reset'),
-            dataType: 'json',
-            data: data,
-            beforeSend: () => {
-                $('#reset-button').html(
-                    '<i class="fa fa-spinner fa-spin"></i> ' + trans('auth.resetting')
-                ).prop('disabled', 'disabled');
-            }
-        }).then(({ errno, msg }) => {
+    })(data, async () => {
+        try {
+            const { errno, msg } = await fetch({
+                type: 'POST',
+                url: url('auth/reset'),
+                dataType: 'json',
+                data: data,
+                beforeSend: () => {
+                    $('#reset-button').html(
+                        '<i class="fa fa-spinner fa-spin"></i> ' + trans('auth.resetting')
+                    ).prop('disabled', 'disabled');
+                }
+            });
             if (errno == 0) {
                 swal({
                     type: 'success',
@@ -46,9 +47,9 @@ $('#reset-button').click(e => {
                 showMsg(msg, 'warning');
                 $('#reset-button').html(trans('auth.reset')).prop('disabled', '');
             }
-        }).catch(err => {
-            showAjaxError(err);
+        } catch (error) {
+            showAjaxError(error);
             $('#reset-button').html(trans('auth.reset')).prop('disabled', '');
-        });
+        }
     });
 });
diff --git a/resources/assets/src/js/common/logout.js b/resources/assets/src/js/common/logout.js
index 244adf44..b099894a 100644
--- a/resources/assets/src/js/common/logout.js
+++ b/resources/assets/src/js/common/logout.js
@@ -1,21 +1,28 @@
 'use strict';
 
-function confirmLogout() {
-    swal({
-        text: trans('general.confirmLogout'),
-        type: 'warning',
-        showCancelButton: true,
-        confirmButtonText: trans('general.confirm'),
-        cancelButtonText: trans('general.cancel')
-    }).then(() => {
-        logout().then(json => {
-            swal({
-                type: 'success',
-                html: json.msg
-            });
-            window.setTimeout(() => window.location = url(), 1000);
+async function confirmLogout() {
+    try {
+        await swal({
+            text: trans('general.confirmLogout'),
+            type: 'warning',
+            showCancelButton: true,
+            confirmButtonText: trans('general.confirm'),
+            cancelButtonText: trans('general.cancel')
         });
-    });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { msg } = await logout();
+        setTimeout(() => window.location = url(), 1000);
+        swal({
+            type: 'success',
+            html: msg
+        });
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 function logout() {
diff --git a/resources/assets/src/js/skinlib/index.js b/resources/assets/src/js/skinlib/index.js
index 73d26d0b..b29ac0b7 100644
--- a/resources/assets/src/js/skinlib/index.js
+++ b/resources/assets/src/js/skinlib/index.js
@@ -79,16 +79,20 @@ function renderSkinlib(items) {
     $('.overlay').hide();
 }
 
-function reloadSkinlib() {
-    requestSkinlibData().then(result => {
+async function reloadSkinlib() {
+    try {
+        const result = await requestSkinlibData();
+
         $('.overlay').show();
         renderSkinlib(result.items);
 
         updatePaginator($.skinlib.page, result.total_pages || 1);
-    }).then(() => {
+
         updateUrlQueryString();
         updateBreadCrumb();
-    });
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 function requestSkinlibData() {
diff --git a/resources/assets/src/js/skinlib/operations.js b/resources/assets/src/js/skinlib/operations.js
index 6caed97f..32b8aa16 100644
--- a/resources/assets/src/js/skinlib/operations.js
+++ b/resources/assets/src/js/skinlib/operations.js
@@ -14,31 +14,38 @@ $(document).on('click', '.more.like', function () {
 });
 
 function addToCloset(tid) {
-    $.getJSON(url(`skinlib/info/${tid}`), ({ name }) => {
-        swal({
-            title: trans('skinlib.setItemName'),
-            inputValue: name,
-            input: 'text',
-            showCancelButton: true,
-            inputValidator: value => (new Promise((resolve, reject) => {
-                value ? resolve() : reject(trans('skinlib.emptyItemName'));
-            }))
-        }).then(result => ajaxAddToCloset(tid, result));
+    $.getJSON(url(`skinlib/info/${tid}`), async ({ name }) => {
+        try {
+            const result = await swal({
+                title: trans('skinlib.setItemName'),
+                inputValue: name,
+                input: 'text',
+                showCancelButton: true,
+                inputValidator: value => (new Promise((resolve, reject) => {
+                    value ? resolve() : reject(trans('skinlib.emptyItemName'));
+                }))
+            });
+            ajaxAddToCloset(tid, result);
+        } catch (error) {
+            //
+        }
     });
 }
 
-function ajaxAddToCloset(tid, name) {
+async function ajaxAddToCloset(tid, name) {
     // Remove interference of modal which is hide
     $('.modal').each(function () {
         return ($(this).css('display') == 'none') ? $(this).remove() : null;
     });
 
-    fetch({
-        type: 'POST',
-        url: url('user/closet/add'),
-        dataType: 'json',
-        data: { tid: tid, name: name }
-    }).then(({ errno, msg }) => {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/closet/add'),
+            dataType: 'json',
+            data: { tid: tid, name: name }
+        });
+
         if (errno == 0) {
             swal({ type: 'success', html: msg });
 
@@ -47,22 +54,32 @@ function ajaxAddToCloset(tid, name) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function removeFromCloset(tid) {
-    swal({
-        text: trans('user.removeFromClosetNotice'),
-        type: 'warning',
-        showCancelButton: true,
-        cancelButtonColor: '#3085d6',
-        confirmButtonColor: '#d33'
-    }).then(() => fetch({
-        type: 'POST',
-        url: url('/user/closet/remove'),
-        dataType: 'json',
-        data: { tid: tid }
-    })).then(({ errno, msg }) => {
+async function removeFromCloset(tid) {
+    try {
+        await swal({
+            text: trans('user.removeFromClosetNotice'),
+            type: 'warning',
+            showCancelButton: true,
+            cancelButtonColor: '#3085d6',
+            confirmButtonColor: '#d33'
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('/user/closet/remove'),
+            dataType: 'json',
+            data: { tid: tid }
+        });
+
         if (errno == 0) {
             swal({ type: 'success', html: msg });
 
@@ -70,33 +87,45 @@ function removeFromCloset(tid) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function changeTextureName(tid, oldName) {
+async function changeTextureName(tid, oldName) {
     let newTextureName = '';
 
-    swal({
-        text: trans('skinlib.setNewTextureName'),
-        input: 'text',
-        inputValue: oldName,
-        showCancelButton: true,
-        inputValidator: value => (new Promise((resolve, reject) => {
-            (newTextureName = value) ? resolve() : reject(trans('skinlib.emptyNewTextureName'));
-        }))
-    }).then(name => fetch({
-        type: 'POST',
-        url: url('skinlib/rename'),
-        dataType: 'json',
-        data: { tid: tid, new_name: name }
-    })).then(({ errno, msg }) => {
+    try {
+        newTextureName = await swal({
+            text: trans('skinlib.setNewTextureName'),
+            input: 'text',
+            inputValue: oldName,
+            showCancelButton: true,
+            inputValidator: value => (new Promise((resolve, reject) => {
+                value ? resolve() : reject(trans('skinlib.emptyNewTextureName'));
+            }))
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('skinlib/rename'),
+            dataType: 'json',
+            data: { tid: tid, new_name: newTextureName }
+        });
+
         if (errno == 0) {
             $('#name').text(newTextureName);
             toastr.success(msg);
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 /**
@@ -120,25 +149,30 @@ function updateTextureStatus(tid, action) {
     $('#likes').html(likes);
 }
 
-$(document).on('click', '.private-label', function () {
-    swal({
-        text: trans('skinlib.setPublicNotice'),
-        type: 'warning',
-        showCancelButton: true
-    }).then(() => {
+$(document).on('click', '.private-label', async function () {
+    try {
+        await swal({
+            text: trans('skinlib.setPublicNotice'),
+            type: 'warning',
+            showCancelButton: true
+        });
+
         changePrivacy($(this).attr('tid'));
         $(this).remove();
-    });
+    } catch (error) {
+        //
+    }
 });
 
-function changePrivacy(tid) {
-    fetch({
-        type: 'POST',
-        url: url('skinlib/privacy'),
-        dataType: 'json',
-        data: { tid: tid }
-    }).then(result => {
-        let { errno, msg } = result;
+async function changePrivacy(tid) {
+    try {
+        const result = await fetch({
+            type: 'POST',
+            url: url('skinlib/privacy'),
+            dataType: 'json',
+            data: { tid: tid }
+        });
+        const { errno, msg } = result;
 
         if (errno == 0) {
             toastr.success(msg);
@@ -151,28 +185,39 @@ function changePrivacy(tid) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function deleteTexture(tid) {
-    swal({
-        text: trans('skinlib.deleteNotice'),
-        type: 'warning',
-        showCancelButton: true
-    }).then(() => fetch({
-        type: 'POST',
-        url: url('skinlib/delete'),
-        dataType: 'json',
-        data: { tid: tid }
-    })).then(({ errno, msg }) => {
+async function deleteTexture(tid) {
+    try {
+        await swal({
+            text: trans('skinlib.deleteNotice'),
+            type: 'warning',
+            showCancelButton: true
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('skinlib/delete'),
+            dataType: 'json',
+            data: { tid: tid }
+        });
+
         if (errno == 0) {
-            swal({ type: 'success', html: msg }).then(() => {
-                window.location = url('skinlib');
-            });
+            await swal({ type: 'success', html: msg });
+            window.location = url('skinlib');
         } else {
             swal({ type: 'warning', html: msg });
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 if (typeof require !== 'undefined' && typeof module !== 'undefined') {
diff --git a/resources/assets/src/js/skinlib/upload.js b/resources/assets/src/js/skinlib/upload.js
index ebb857c6..15d92823 100644
--- a/resources/assets/src/js/skinlib/upload.js
+++ b/resources/assets/src/js/skinlib/upload.js
@@ -85,25 +85,27 @@ function upload() {
         } else {
             callback();
         }
-    })(form, file, () => {
-        fetch({
-            type: 'POST',
-            url: url('skinlib/upload'),
-            contentType: false,
-            dataType: 'json',
-            data: form,
-            processData: false,
-            beforeSend: () => {
-                $('#upload-button').html(
-                    '<i class="fa fa-spinner fa-spin"></i> ' + trans('skinlib.uploading')
-                ).prop('disabled', 'disabled');
-            }
-        }).then(({ errno, msg, tid }) => {
+    })(form, file, async () => {
+        try {
+            const { errno, msg, tid } = await fetch({
+                type: 'POST',
+                url: url('skinlib/upload'),
+                contentType: false,
+                dataType: 'json',
+                data: form,
+                processData: false,
+                beforeSend: () => {
+                    $('#upload-button').html(
+                        '<i class="fa fa-spinner fa-spin"></i> ' + trans('skinlib.uploading')
+                    ).prop('disabled', 'disabled');
+                }
+            });
+
             if (errno == 0) {
                 let redirect = function () {
                     toastr.info(trans('skinlib.redirecting'));
 
-                    window.setTimeout(() => {
+                    setTimeout(() => {
                         window.location = url(`skinlib/show/${tid}`);
                     }, 1000);
                 };
@@ -114,17 +116,16 @@ function upload() {
                     html: msg
                 }).then(redirect, redirect);
             } else {
-                swal({
+                await swal({
                     type: 'warning',
                     html: msg
-                }).then(() => {
-                    $('#upload-button').html(trans('skinlib.upload')).prop('disabled', '');
                 });
+                $('#upload-button').html(trans('skinlib.upload')).prop('disabled', '');
             }
-        }).catch(err => {
-            showAjaxError(err);
+        } catch (error) {
+            showAjaxError(error);
             $('#upload-button').html(trans('skinlib.upload')).prop('disabled', '');
-        });
+        }
     });
 }
 
diff --git a/resources/assets/src/js/user/closet.js b/resources/assets/src/js/user/closet.js
index 793f9f89..8f9685d4 100644
--- a/resources/assets/src/js/user/closet.js
+++ b/resources/assets/src/js/user/closet.js
@@ -4,17 +4,24 @@
 
 var selectedTextures = [];
 
-$(document).ready(function () {
+$(document).ready(async function () {
     if (! window.location.pathname.includes('/user/closet'))
         return;
 
-    fetch({
-        type: 'GET',
-        url: url('/user/closet-data'),
-        dataType: 'json'
-    }).then(({ items, category, total_pages }) => {
-        renderCloset(items, category);
+    $('input[name=q]').on('input', debounce(() => {
+        let category = $('#skin-category').hasClass('active') ? 'skin' : 'cape';
+        reloadCloset(category, 1, $('input[name=q]').val());
+    }, 350));
 
+    try {
+        const { items, category, total_pages } = await fetch({
+            type: 'GET',
+            url: url('/user/closet-data'),
+            dataType: 'json'
+        });
+
+        renderCloset(items, category);
+        
         $('#closet-paginator').jqPaginator($.extend({}, $.defaultPaginatorConfig, {
             totalPages: total_pages,
             onPageChange: page => reloadCloset(
@@ -22,15 +29,12 @@ $(document).ready(function () {
                 page, $('input[name=q]').val()
             )
         }));
-    }).catch(showAjaxError);
-
-    $('input[name=q]').on('input', debounce(() => {
-        let category = $('#skin-category').hasClass('active') ? 'skin' : 'cape';
-        reloadCloset(category, 1, $('input[name=q]').val());
-    }, 350));
+    } catch (error) {
+        showAjaxError(error);
+    }
 });
 
-$('body').on('click', '.item-body', function () {
+$('body').on('click', '.item-body', async function () {
     $('.item-selected').parent().removeClass('item-selected');
     let $item = $(this).parent();
 
@@ -38,11 +42,13 @@ $('body').on('click', '.item-body', function () {
 
     let tid = parseInt($item.attr('tid'));
 
-    fetch({
-        type: 'POST',
-        url: url(`skinlib/info/${tid}`),
-        dataType: 'json'
-    }).then(({ type, hash }) => {
+    try {
+        const { type, hash } = await fetch({
+            type: 'POST',
+            url: url(`skinlib/info/${tid}`),
+            dataType: 'json'
+        });
+
         if (type == 'cape') {
             MSP.changeCape(url(`textures/${hash}`));
             selectedTextures['cape'] = tid;
@@ -63,7 +69,9 @@ $('body').on('click', '.item-body', function () {
         } else if (cape != undefined) {
             $indicator.text(trans('general.cape'));
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 });
 
 $('body').on('click', '.category-switch', () => {
@@ -131,31 +139,35 @@ function renderCloset(items, category) {
  * Reload and render closet.
  *
  * @param {string} category
- * @param {integer} page
+ * @param {number} page
  * @param {string} search
  */
-function reloadCloset(category, page, search) {
-    fetch({
-        type: 'GET',
-        url: url('user/closet-data'),
-        dataType: 'json',
-        data: {
-            category: category,
-            page: page,
-            perPage: getCapacityOfCloset(),
-            q: search
-        }
-    }).then(({ items, category, total_pages }) => {
+async function reloadCloset(textureCategory, page, search) {
+    try {
+        const { items, category, total_pages } = await fetch({
+            type: 'GET',
+            url: url('user/closet-data'),
+            dataType: 'json',
+            data: {
+                category: textureCategory,
+                page: page,
+                perPage: getCapacityOfCloset(),
+                q: search
+            }
+        });
+
         renderCloset(items, category);
-
+        
         let paginator = $('#closet-paginator');
-
+        
         paginator.attr(`last-${category}-page`, page);
         paginator.jqPaginator('option', {
             currentPage: page,
             totalPages: total_pages
         });
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 /**
@@ -170,23 +182,31 @@ function getCapacityOfCloset() {
     ) * 2;
 }
 
-function renameClosetItem(tid, oldName) {
+async function renameClosetItem(tid, oldName) {
     let newTextureName = '';
 
-    swal({
-        title: trans('user.renameClosetItem'),
-        input: 'text',
-        inputValue: oldName,
-        showCancelButton: true,
-        inputValidator: value => (new Promise((resolve, reject) => {
-            (newTextureName = value) ? resolve() : reject(trans('skinlib.emptyNewTextureName'));
-        }))
-    }).then(name => fetch({
-        type: 'POST',
-        url: url('user/closet/rename'),
-        dataType: 'json',
-        data: { tid: tid, new_name: name }
-    })).then(({ errno, msg }) => {
+    try {
+        newTextureName = await swal({
+            title: trans('user.renameClosetItem'),
+            input: 'text',
+            inputValue: oldName,
+            showCancelButton: true,
+            inputValidator: value => (new Promise((resolve, reject) => {
+                value ? resolve() : reject(trans('skinlib.emptyNewTextureName'));
+            }))
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/closet/rename'),
+            dataType: 'json',
+            data: { tid: tid, new_name: newTextureName }
+        });
+
         if (errno == 0) {
             const type = $(`[tid=${tid}]`).data('texture-type');
             $(`[tid=${tid}]>.item-footer>.texture-name>span`).html(
@@ -197,20 +217,30 @@ function renameClosetItem(tid, oldName) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function removeFromCloset(tid) {
-    swal({
-        text: trans('user.removeFromClosetNotice'),
-        type: 'warning',
-        showCancelButton: true
-    }).then(() => fetch({
-        type: 'POST',
-        url: url('user/closet/remove'),
-        dataType: 'json',
-        data: { tid: tid }
-    })).then(({ errno, msg }) => {
+async function removeFromCloset(tid) {
+    try {
+        await swal({
+            text: trans('user.removeFromClosetNotice'),
+            type: 'warning',
+            showCancelButton: true
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/closet/remove'),
+            dataType: 'json',
+            data: { tid: tid }
+        });
+
         if (errno == 0) {
             swal({ type: 'success', html: msg });
 
@@ -227,21 +257,31 @@ function removeFromCloset(tid) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function setAsAvatar(tid) {
-    swal({
-        title: trans('user.setAvatar'),
-        text: trans('user.setAvatarNotice'),
-        type: 'question',
-        showCancelButton: true
-    }).then(() => fetch({
-        type: 'POST',
-        url: url('user/profile/avatar'),
-        dataType: 'json',
-        data: { tid: tid }
-    })).then(({ errno, msg }) => {
+async function setAsAvatar(tid) {
+    try {
+        await swal({
+            title: trans('user.setAvatar'),
+            text: trans('user.setAvatarNotice'),
+            type: 'question',
+            showCancelButton: true
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/profile/avatar'),
+            dataType: 'json',
+            data: { tid: tid }
+        });
+
         if (errno == 0) {
             toastr.success(msg);
 
@@ -252,7 +292,9 @@ function setAsAvatar(tid) {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 if (typeof require !== 'undefined' && typeof module !== 'undefined') {
diff --git a/resources/assets/src/js/user/player.js b/resources/assets/src/js/user/player.js
index 3f99e39d..406818cb 100644
--- a/resources/assets/src/js/user/player.js
+++ b/resources/assets/src/js/user/player.js
@@ -9,24 +9,29 @@ $('body').on('click', '.player', function () {
     showPlayerTexturePreview(this.id);
 }).on('click', '#preview-switch', () => {
     TexturePreview.previewType == '3D' ? TexturePreview.show2dPreview() : TexturePreview.show3dPreview();
-}).on('change', '#preference', function () {
-    fetch({
-        type: 'POST',
-        url: url('user/player/preference'),
-        dataType: 'json',
-        data: { pid: $(this).attr('pid'), preference: $(this).val() }
-    }).then(({ errno, msg }) => {
-        (errno == 0) ? toastr.success(msg) : toastr.warning(msg);
-    }).catch(showAjaxError);
+}).on('change', '#preference', async function () {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/player/preference'),
+            dataType: 'json',
+            data: { pid: $(this).attr('pid'), preference: $(this).val() }
+        });
+        errno == 0 ? toastr.success(msg) : toastr.warning(msg);
+    } catch (error) {
+        showAjaxError(error);
+    }
 });
 
-function showPlayerTexturePreview(pid) {
-    fetch({
-        type: 'POST',
-        url: url('user/player/show'),
-        dataType: 'json',
-        data: { pid: pid }
-    }).then(result => {
+async function showPlayerTexturePreview(pid) {
+    try {
+        const result = await fetch({
+            type: 'POST',
+            url: url('user/player/show'),
+            dataType: 'json',
+            data: { pid: pid }
+        });
+
         // Render skin preview of selected player
         ['steve', 'alex', 'cape'].forEach((type) => {
             let tid     = result[`tid_${type}`];
@@ -47,37 +52,48 @@ function showPlayerTexturePreview(pid) {
         }
 
         console.log(`Texture previews of player ${result.player_name} rendered.`);
-
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function changePlayerName(pid) {
+async function changePlayerName(pid) {
     let newPlayerName = '';
     const $playerName = $(`td:contains("${pid}")`).next();
 
-    swal({
-        title: trans('user.changePlayerName'),
-        text: $('#player_name').attr('placeholder'),
-        inputValue: $playerName.html(),
-        input: 'text',
-        showCancelButton: true,
-        inputValidator: value => (new Promise((resolve, reject) => {
-            (newPlayerName = value) ? resolve() : reject(trans('skinlib.emptyPlayerName'));
-        }))
-    }).then(name => fetch({
-        type: 'POST',
-        url: url('user/player/rename'),
-        dataType: 'json',
-        data: { pid: pid, new_player_name: name }
-    })).then(({ errno, msg }) => {
+    try {
+        newPlayerName = await swal({
+            title: trans('user.changePlayerName'),
+            text: $('#player_name').attr('placeholder'),
+            inputValue: $playerName.html(),
+            input: 'text',
+            showCancelButton: true,
+            inputValidator: value => (new Promise((resolve, reject) => {
+                value ? resolve() : reject(trans('skinlib.emptyPlayerName'));
+            }))
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/player/rename'),
+            dataType: 'json',
+            data: { pid: pid, new_player_name: newPlayerName }
+        });
+
         if (errno == 0) {
             swal({ type: 'success', html: msg });
 
             $playerName.html(newPlayerName);
         } else {
-            swal({ type: 'error', html: msg });
+            swal({ type: 'warning', html: msg });
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 function clearTexture(pid) {
@@ -99,7 +115,7 @@ function clearTexture(pid) {
     });
 }
 
-function ajaxClearTexture(pid) {
+async function ajaxClearTexture(pid) {
     $('.modal').each(function () {
         if ($(this).css('display') == 'none') $(this).remove();
     });
@@ -114,49 +130,65 @@ function ajaxClearTexture(pid) {
         return toastr.warning(trans('user.noClearChoice'));
     }
 
-    fetch({
-        type: 'POST',
-        url: url('user/player/texture/clear'),
-        dataType: 'json',
-        data: data
-    }).then(({ errno, msg }) => {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/player/texture/clear'),
+            dataType: 'json',
+            data: data
+        });
         swal({ type: errno == 0 ? 'success' : 'error', html: msg });
         $('.modal').modal('hide');
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function deletePlayer(pid) {
-    swal({
-        title: trans('user.deletePlayer'),
-        text: trans('user.deletePlayerNotice'),
-        type: 'warning',
-        showCancelButton: true,
-        cancelButtonColor: '#3085d6',
-        confirmButtonColor: '#d33'
-    }).then(() => fetch({
-        type: 'POST',
-        url: url('user/player/delete'),
-        dataType: 'json',
-        data: { pid: pid }
-    })).then(({ errno, msg }) => {
+async function deletePlayer(pid) {
+    try {
+        await swal({
+            title: trans('user.deletePlayer'),
+            text: trans('user.deletePlayerNotice'),
+            type: 'warning',
+            showCancelButton: true,
+            cancelButtonColor: '#3085d6',
+            confirmButtonColor: '#d33'
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/player/delete'),
+            dataType: 'json',
+            data: { pid: pid }
+        });
+
         if (errno == 0) {
-            swal({
+            await swal({
                 type: 'success',
                 html: msg
-            }).then(() => $(`tr#${pid}`).remove());
+            });
+            $(`tr#${pid}`).remove();
         } else {
-            swal({ type: 'error', html: msg });
+            toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function addNewPlayer() {
-    fetch({
-        type: 'POST',
-        url: url('user/player/add'),
-        dataType: 'json',
-        data: { player_name: $('#player_name').val() }
-    }).then(({ errno, msg }) => {
+async function addNewPlayer() {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/player/add'),
+            dataType: 'json',
+            data: { player_name: $('#player_name').val() }
+        });
+
         if (errno == 0) {
             swal({
                 type: 'success',
@@ -167,10 +199,12 @@ function addNewPlayer() {
         } else {
             toastr.warning(msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function setTexture() {
+async function setTexture() {
     let pid = 0,
         skin = selectedTextures['skin'],
         cape = selectedTextures['cape'];
@@ -184,23 +218,27 @@ function setTexture() {
     } else if (skin == undefined && cape == undefined) {
         toastr.info(trans('user.emptySelectedTexture'));
     } else {
-        fetch({
-            type: 'POST',
-            url: url('user/player/set'),
-            dataType: 'json',
-            data: {
-                'pid': pid,
-                'tid[skin]': skin,
-                'tid[cape]': cape
-            }
-        }).then(({ errno, msg }) => {
+        try {
+            const { errno, msg } = await fetch({
+                type: 'POST',
+                url: url('user/player/set'),
+                dataType: 'json',
+                data: {
+                    'pid': pid,
+                    'tid[skin]': skin,
+                    'tid[cape]': cape
+                }
+            });
+
             if (errno == 0) {
                 swal({ type: 'success', html: msg });
                 $('#modal-use-as').modal('hide');
             } else {
                 toastr.warning(msg);
             }
-        }).catch(showAjaxError);
+        } catch (error) {
+            showAjaxError(error);
+        }
     }
 }
 
diff --git a/resources/assets/src/js/user/profile.js b/resources/assets/src/js/user/profile.js
index ccb82f8c..e94b3f7a 100644
--- a/resources/assets/src/js/user/profile.js
+++ b/resources/assets/src/js/user/profile.js
@@ -1,22 +1,30 @@
 'use strict';
 
-function changeNickName() {
+async function changeNickName() {
     let name = $('#new-nickname').val();
 
     if (! name) {
         return swal({ type: 'error', html: trans('user.emptyNewNickName') });
     }
 
-    swal({
-        text: trans('user.changeNickName', { new_nickname: name }),
-        type: 'question',
-        showCancelButton: true
-    }).then(() => fetch({
-        type: 'POST',
-        url: url('user/profile?action=nickname'),
-        dataType: 'json',
-        data: { new_nickname: name }
-    })).then(({ errno, msg }) => {
+    try {
+        await swal({
+            text: trans('user.changeNickName', { new_nickname: name }),
+            type: 'question',
+            showCancelButton: true
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/profile?action=nickname'),
+            dataType: 'json',
+            data: { new_nickname: name }
+        });
+
         if (errno == 0) {
 
             $('.nickname').each(function () {
@@ -27,10 +35,12 @@ function changeNickName() {
         } else {
             return swal({ type: 'warning', html: msg });
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function changePassword() {
+async function changePassword() {
     let $oldPasswd = $('#password'),
         $newPasswd = $('#new-passwd'),
         $confirmPwd = $('#confirm-pwd');
@@ -51,25 +61,33 @@ function changePassword() {
         toastr.warning(trans('auth.invalidConfirmPwd'));
         $confirmPwd.focus();
     } else {
-        fetch({
-            type: 'POST',
-            url: url('user/profile?action=password'),
-            dataType: 'json',
-            data: { 'current_password': password, 'new_password': newPasswd }
-        }).then(({ errno, msg }) => {
+        try {
+            const { errno, msg } = await fetch({
+                type: 'POST',
+                url: url('user/profile?action=password'),
+                dataType: 'json',
+                data: { 'current_password': password, 'new_password': newPasswd }
+            });
+
             if (errno == 0) {
-                return swal({
-                    type: 'success',
-                    text: msg
-                }).then(() => logout()).catch(err => {
-                    docCookies.removeItem('token') && console.warn(err);
-                }).then(() => {
+                try {
+                    await swal({
+                        type: 'success',
+                        text: msg
+                    });
+                    await logout();
+                } catch (error) {
+                    docCookies.removeItem('token') && console.warn(error);
+                } finally {
                     window.location = url('auth/login');
-                });
+                }
+                return;
             } else {
                 return swal({ type: 'warning', text: msg });
             }
-        }).catch(showAjaxError);
+        } catch (error) {
+            showAjaxError(error);
+        }
     }
 }
 
@@ -83,8 +101,8 @@ $('#new-email').focusin(() => {
     }
 }, 10));
 
-function changeEmail() {
-    var newEmail = $('#new-email').val();
+async function changeEmail() {
+    const newEmail = $('#new-email').val();
 
     if (! newEmail) {
         return swal({ type: 'error', html: trans('user.emptyNewEmail') });
@@ -95,55 +113,72 @@ function changeEmail() {
         return swal({ type: 'warning', html: trans('auth.invalidEmail') });
     }
 
-    swal({
-        text: trans('user.changeEmail', { new_email: newEmail }),
-        type: 'question',
-        showCancelButton: true
-    }).then(() => fetch({
-        type: 'POST',
-        url: url('user/profile?action=email'),
-        dataType: 'json',
-        data: { new_email: newEmail, password: $('#current-password').val() }
-    })).then(({ errno, msg }) => {
+    try {
+        await swal({
+            text: trans('user.changeEmail', { new_email: newEmail }),
+            type: 'question',
+            showCancelButton: true
+        });
+    } catch (error) {
+        return;
+    }
+
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/profile?action=email'),
+            dataType: 'json',
+            data: { new_email: newEmail, password: $('#current-password').val() }
+        });
+
         if (errno == 0) {
-            return swal({
+            await swal({
                 type: 'success',
                 text: msg
-            }).then(() => logout()).catch(err => {
-                docCookies.removeItem('token') && console.warn(err);
-            }).then(() => {
-                window.location = url('auth/login');
             });
+            
+            try {
+                await logout();
+            } catch (error) {
+                docCookies.removeItem('token') && console.warn(error);
+            } finally {
+                window.location = url('auth/login');
+            }
         } else {
             return swal({ type: 'warning', text: msg });
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
-function deleteAccount() {
+async function deleteAccount() {
     let password = $('.modal-body>#password').val();
 
     if (! password) {
         return swal({ type: 'warning', html: trans('user.emptyDeletePassword') });
     }
 
-    fetch({
-        type: 'POST',
-        url: url('user/profile?action=delete'),
-        dataType: 'json',
-        data: { password: password }
-    }).then(({ errno, msg }) => {
+    try {
+        const { errno, msg } = await fetch({
+            type: 'POST',
+            url: url('user/profile?action=delete'),
+            dataType: 'json',
+            data: { password: password }
+        });
+
         if (errno == 0) {
-            return swal({
+            await swal({
                 type: 'success',
                 html: msg
-            }).then(() => {
-                window.location = url('auth/login');
             });
+            window.location = url('auth/login');
         } else {
             return swal({ type: 'warning', html: msg });
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 if (typeof require !== 'undefined' && typeof module !== 'undefined') {
diff --git a/resources/assets/src/js/user/sign.js b/resources/assets/src/js/user/sign.js
index 6dc90718..27ff443e 100644
--- a/resources/assets/src/js/user/sign.js
+++ b/resources/assets/src/js/user/sign.js
@@ -1,9 +1,11 @@
-function sign() {
-    fetch({
-        type: 'POST',
-        url: url('user/sign'),
-        dataType: 'json'
-    }).then(result => {
+async function sign() {
+    try {
+        const result = await fetch({
+            type: 'POST',
+            url: url('user/sign'),
+            dataType: 'json'
+        });
+
         if (result.errno == 0) {
             $('#score').html(result.score);
             const dom = '<i class="fa fa-calendar-check-o"></i> &nbsp;' + trans(
@@ -29,7 +31,9 @@ function sign() {
         } else {
             toastr.warning(result.msg);
         }
-    }).catch(showAjaxError);
+    } catch (error) {
+        showAjaxError(error);
+    }
 }
 
 if (typeof require !== 'undefined' && typeof module !== 'undefined') {
diff --git a/yarn.lock b/yarn.lock
index f2ea9ab2..b80699ae 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2978,6 +2978,10 @@ meow@^3.7.0:
     redent "^1.0.0"
     trim-newlines "^1.0.0"
 
+merge2@^1.2.0:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/merge2/-/merge2-1.2.0.tgz#0f882151d988b1f3d0758945404fa73ee5923d3f"
+
 merge@^1.1.3:
   version "1.2.0"
   resolved "http://registry.npm.taobao.org/merge/download/merge-1.2.0.tgz#7531e39d4949c281a66b8c5a6e0265e8b05894da"