Does it mutate 😱

Array.prototype.toString

No mutation

Description

The toString() method returns a string representing the specified array and its elements.

Array.prototype.toString ( )

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

Example

var array1 = [1, 2, 'a', '1a'];

console.log(array1.toString());
// expected output: "1,2,a,1a"