index

Zero-based index at which to change the array,converted to an integer.

• Negative index counts back from the end of the array — if-array.length <= index < 0,index + array.length is used.
• If the index after normalization is out of bounds, aRangeError is thrown.

value

Any value to be assigned to the given index.

A new array with the element atindex replaced withvalue.

RangeError

Thrown ifindex >= array.length orindex < -array.length.

Thewith() method changes the value of a given index in the array, returning a new array with the element at the given index replaced with the given value. The original array is not modified. This allows you to chain array methods while doing manipulations.

By combiningwith() withat(), you can both write and read (respectively) an array using negative indices.

Thewith() method never produces asparse array. If the source array is sparse, the empty slots will be replaced withundefined in the new array.

Thewith() method isgeneric. It only expects thethis value to have alength property and integer-keyed properties.

With thewith() method, you can update a single element in an array and then apply other array methods.

const arr = [1, 2, 3, 4, 5];console.log(arr.with(2, 6).map((x) => x ** 2)); // [1, 4, 36, 16, 25]

Thewith() method always creates a dense array.

const arr = [1, , 3, 4, , 6];console.log(arr.with(0, 2)); // [2, undefined, 3, 4, undefined, 6]

Thewith() method creates and returns a new array. It reads thelength property ofthis and then accesses each property whose key is a nonnegative integer less thanlength. As each property ofthis is accessed, the array element having an index equal to the key of the property is set to the value of the property. Finally, the array value atindex is set tovalue.

const arrayLike = {  length: 3,  unrelated: "foo",  0: 5,  2: 4,  3: 3, // ignored by with() since length is 3};console.log(Array.prototype.with.call(arrayLike, 0, 1));// [ 1, undefined, 4 ]

• Polyfill ofArray.prototype.with incore-js
• es-shims polyfill ofArray.prototype.with
• Indexed collections guide
• Array.prototype.toReversed()
• Array.prototype.toSorted()
• Array.prototype.toSpliced()
• Array.prototype.at()
• TypedArray.prototype.with()