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

Here is how I'd like to do it:

function update(array, newItem, atIndex) {
    return array.map((item, index) => index === atIndex ? newItem : item);
}

Generally, Array-spread operation produces few temporary arrays for you, but map doesn't, so it can be faster. You can also look at this discussion as a reference