JavaScript - copy array with replace item operation

In this article, we would like to show you how to copy an array with item replace operation using JavaScript.

Quick solution:

// ONLINE-RUNNER:browser;

var array = [1, 2, 3];
var index = 1;
var replacement = 4;

var result = array.map((value, i) => (i === index ? replacement : value));

console.log(result);  // [1, 4, 3]

Reusable function example

In this example, we create a reusable function that creates a copy of the given array and replaces the item with given index with the replacement.

// ONLINE-RUNNER:browser;

function replaceItem(array, index, replacement) {
    return array.map((value, i) => (i === index ? replacement : value));
}


// Usage example:

var array = [1, 2, 3];

var copy1 = replaceItem(array, 0, 4);
var copy2 = replaceItem(array, 0, 5);

var copy3 = replaceItem(array, 1, 6);
var copy4 = replaceItem(array, 1, 7);

console.log(copy1);  // [ 4, 2, 3 ]
console.log(copy2);  // [ 5, 2, 3 ]

console.log(copy3);  // [ 1, 6, 3 ]
console.log(copy4);  // [ 1, 7, 3 ]

See also

1. JavaScript - copy array with append item operation

2. JavaScript - copy array with prepend item operation

3. JavaScript - copy array with remove item operation

References

1. Array.prototype.map() - JavaScript | MDN