Does it mutate 😱

Array.prototype.copyWithin

Mutates

Description

The copyWithin() method of Array instances shallow copies part of this array to another location in the same array and returns this array without modifying its length.

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

Example

const array1 = ['a', 'b', 'c', 'd', 'e'];

// Copy to index 0 the element at index 3
console.log(array1.copyWithin(0, 3, 4));
// Expected output: Array ["d", "b", "c", "d", "e"]

// Copy to index 1 all elements from index 3 to the end
console.log(array1.copyWithin(1, 3));
// Expected output: Array ["d", "d", "e", "d", "e"]