How to count the occurrences of a value in an array in JavaScript

In this Article we will go through how to count the occurrences of a value in an array only using single line of code in JavaScript. This is a one-line JavaScript code snippet that uses one of the most popular ES6 features => Arrow Function.

Let's define this short function:

const countOccurrences = (arr, val) => arr.reduce((a, v) => (v === val ? a + 1 : a), 0);

const countOccurrences = (arr, val) => arr.filter(item => item === val).length;

countOccurrences([2, 1, 3, 3, 2, 3], 2);                // 2
countOccurrences(['a', 'b', 'a', 'c', 'a', 'b'], 'a');  // 3