How to create an array of cumulative sum in JavaScript

In this Article we will go through how to create an array of cumulative sum 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 accumulate = arr => arr.map((sum => value => sum += value)(0));

const accumulate = arr => arr.reduce((a, b, i) => i === 0 ? [b] : [...a, b + a[i - 1]], []);

const accumulate = arr => arr.reduce((a, b, i) => i === 0 ? [b] : [...a, b + a[i - 1]], 0);

accumulate([1, 2, 3, 4]);   // [1, 3, 6, 10]
// 1             = 1
// 1 + 2         = 3
// 1 + 2 + 3     = 6
// 1 + 2 + 3 + 4 = 10