Create an array of cumulative sum

This function generates an array of cumulative sums from the input array.

JavaScript:

let cumulativeSum = arr => arr.map((sum => value => sum += value)(0));

// Example
console.log(cumulativeSum([1, 2, 3, 4])); // [1, 3, 6, 10]
console.log(cumulativeSum([10, 20, 30, 40])); // [10, 30, 60, 100]

TypeScript:

let cumulativeSum = (arr: number[]): number[] => arr.map((sum => value => sum += value)(0));

// Example
console.log(cumulativeSum([1, 2, 3, 4])); // [1, 3, 6, 10]
console.log(cumulativeSum([10, 20, 30, 40])); // [10, 30, 60, 100]