es-toolkit/docs/reference/math/meanBy.md

meanBy

Calculates the average of an array of numbers when applying the getValue function to each element.

If the array is empty, this function returns NaN.

Signature

export function meanBy<T>(items: T[], getValue: (element: T) => number): number;

Parameters

• items (T[]): An array to calculate the average.
• getValue ((item: T) => number): A function that selects a numeric value from each element.

Returns

(number): The average of all the numbers as determined by the getValue function.

Examples

meanBy([{ a: 1 }, { a: 2 }, { a: 3 }], x => x.a); // Returns: 2
meanBy([], x => x.a); // Returns: NaN