23 lines
789 B
JavaScript
23 lines
789 B
JavaScript
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import { sumBy } from "./sumBy.mjs";
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//#region src/math/meanBy.ts
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/**
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* Calculates the average of an array of numbers when applying
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* the `getValue` 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) => number} getValue A function that selects a numeric value from each element.
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* @returns {number} The average of all the numbers as determined by the `getValue` 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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*/
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function meanBy(items, getValue) {
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return sumBy(items, (item) => getValue(item)) / items.length;
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}
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//#endregion
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export { meanBy };
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