averageBy

JavaScript, Math, Array

Calculates the average of an array, after mapping each element to a value using the provided function.

  • Use Array.prototype.map() to map each element to the value returned by fn.
  • Use Array.prototype.reduce() to add each value to an accumulator, initialized with a value of 0.
  • Divide the resulting array by its length.
const averageBy = (arr, fn) =>
  arr
    .map(typeof fn === 'function' ? fn : val => val[fn])
    .reduce((acc, val) => acc + val, 0) / arr.length;
averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], o => o.n); // 5
averageBy([{ n: 4 }, { n: 2 }, { n: 8 }, { n: 6 }], 'n'); // 5

Recommended snippets

  • sumBy

    JavaScript, Math

    Calculates the sum of an array, after mapping each element to a value using the provided function.

  • maxBy

    JavaScript, Math

    Returns the maximum value of an array, after mapping each element to a value using the provided function.

  • minBy

    JavaScript, Math

    Returns the minimum value of an array, after mapping each element to a value using the provided function.