19 lines
716 B
TypeScript
19 lines
716 B
TypeScript
/**
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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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declare function meanBy<T>(items: readonly T[], getValue: (element: T) => number): number;
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export { meanBy };
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