Add event emitter

resources/assets/src/js/event.js

@@ -0,0 +1,22 @@
+/** @type {{ [name: string]: Function[] }} */
+const bus = Object.create(null);
+
+/**
+ * @param {string} eventName
+ * @param {Function} listener
+ */
+export function on(eventName, listener) {
+    (bus[eventName] || (bus[eventName] = [])).push(listener);
+}
+
+/**
+ * @param {string} eventName
+ * @param {any} payload
+ */
+export function emit(eventName, payload) {
+    bus[eventName] && bus[eventName].forEach(listener => listener(payload));
+}
+
+Object.defineProperty(window, 'bsEmitter', {
+    get: () => Object.freeze({ on, emit })
+});

resources/assets/src/js/index.js

@@ -1,6 +1,7 @@
 import './public-path';  // Must be first
 import './i18n';
 import './net';
+import './event';
 import './layout';
 import './logout';
 import './check-updates';

resources/assets/tests/js/event.test.js

@@ -0,0 +1,18 @@
+import * as emitter from '@/js/event';
+
+test('mount variable to global', () => {
+    expect(window.bsEmitter).toBeFrozen();
+});
+
+test('add listener and emit event', () => {
+    const mockA = jest.fn();
+    const mockB = jest.fn();
+
+    emitter.on('a', mockA);
+    emitter.on('b', mockB);
+
+    emitter.emit('a');
+
+    expect(mockA).toHaveBeenCalledTimes(1);
+    expect(mockB).not.toBeCalled();
+});