28 lines
1.3 KiB
TypeScript
28 lines
1.3 KiB
TypeScript
import { ValueIteratee } from '../_internal/ValueIteratee.mjs';
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/**
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* Calculates the average of an array of numbers when applying
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* the `iteratee` function to each element.
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*
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* If the array is empty, this function returns `NaN`.
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*
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* @template T - The type of elements in the array.
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* @param {T[]} items An array to calculate the average.
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* @param {((element: T) => unknown) | PropertyKey | [PropertyKey, any] | PartialShallow<T>} iteratee
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* The criteria used to determine the maximum value.
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* - If a **function** is provided, it extracts a numeric value from each element.
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* - If a **string** is provided, it is treated as a key to extract values from the objects.
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* - If a **[key, value]** pair is provided, it matches elements with the specified key-value pair.
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* - If an **object** is provided, it matches elements that contain the specified properties.
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* @returns {number} The average of all the numbers as determined by the `iteratee` function.
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*
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* @example
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* meanBy([{ a: 1 }, { a: 2 }, { a: 3 }], x => x.a); // Returns: 2
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* meanBy([], x => x.a); // Returns: NaN
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* meanBy([[2], [3], [1]], 0); // Returns: 2
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* meanBy([{ a: 2 }, { a: 3 }, { a: 1 }], 'a'); // Returns: 2
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*/
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declare function meanBy<T>(items: ArrayLike<T> | null | undefined, iteratee?: ValueIteratee<T>): number;
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export { meanBy };
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