30-seconds-of-code/snippets/js/s/most-frequent-array-element.md

title, type, language, tags, author, cover, dateModified

title	type	language	tags	author	cover	dateModified
Most frequent element in array	snippet	javascript	array	chalarangelo	clock	2020-09-15T16:28:04+03:00

Returns the most frequent element in an array.

• Use Array.prototype.reduce() to map unique values to an object's keys, adding to existing keys every time the same value is encountered.
• Use Object.entries() on the result in combination with Array.prototype.reduce() to get the most frequent value in the array.

const mostFrequent = arr =>
  Object.entries(
    arr.reduce((a, v) => {
      a[v] = a[v] ? a[v] + 1 : 1;
      return a;
    }, {})
  ).reduce((a, v) => (v[1] >= a[1] ? v : a), [null, 0])[0];

mostFrequent(['a', 'b', 'a', 'c', 'a', 'a', 'b']); // 'a'