How to count the occurrences of array elements in JavaScript

In this Article we will go through how to count the occurrences of array elements 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 => arr.reduce((prev, curr) => (prev[curr] = ++prev[curr] || 1, prev), {});

#Example

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