Does it mutate 😱
Array.prototype.reduce
No mutation
Description
The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.
Array.prototype.reduce ( callbackfn [ , initialValue ] )https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce
Example
const array1 = [1, 2, 3, 4];
const reducer = (accumulator, currentValue) => accumulator + currentValue;
// 1 + 2 + 3 + 4
console.log(array1.reduce(reducer));
// expected output: 10
// 5 + 1 + 2 + 3 + 4
console.log(array1.reduce(reducer, 5));
// expected output: 15