Does it mutate 😱

Array.prototype.fill()

Mutates

Description

The fill() method fills all the elements of an array from a start index to an end index with a static value.

arr.fill(value)
arr.fill(value, start)
arr.fill(value, start, end)

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/fill

Example

var array1 = [1, 2, 3, 4];

// fill with 0 from position 2 until position 4
console.log(array1.fill(0, 2, 4));
// expected output: [1, 2, 0, 0]

// fill with 5 from position 1
console.log(array1.fill(5, 1));
// expected output: [1, 5, 5, 5]

console.log(array1.fill(6));
// expected output: [6, 6, 6, 6]