Replace element at specific position in an array without mutating it

Question

How can the following operation be done without mutating the array:

let array = [\'item1\'];
console.log(array); // [\'item1\']
array[2] = \'item2\'; // array is         


        

Answer 1

You can simply set up a a new array as such:

const newItemArray = array.slice();

And then set value for the index which you wish to have a value for.

newItemArray[position] = newItem

and return that. The values under the indexes in-between will have undefined.

Or the obviously alternative would be:

Object.assign([], array, {: newItem});