Atomics.add()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since December 2021.

The Atomics.add() static method adds a given value at a given position in the array and returns the old value at that position. This atomic operation guarantees that no other write happens until the modified value is written back.

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Syntax

Atomics.add(typedArray, index, value)

Parameters

typedArray: An integer typed array. One of Int8Array, Uint8Array, Int16Array, Uint16Array, Int32Array, Uint32Array, BigInt64Array, or BigUint64Array.
index: The position in the typedArray to add a value to.
value: The number to add.

Return value

The old value at the given position (typedArray[index]).

Exceptions

TypeError: Thrown if typedArray is not one of the allowed integer types.
RangeError: Thrown if index is out of bounds in the typedArray.

Examples

Using add()

const sab = new SharedArrayBuffer(1024);
const ta = new Uint8Array(sab);

Atomics.add(ta, 0, 12); // returns 0, the old value
Atomics.load(ta, 0); // 12

Specifications

Specification
ECMAScript Language Specification # sec-atomics.add

Browser compatibility

	Desktop					Mobile						Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	Deno	Node.js
`add`	68	79	78	55	15.2	89	79	63	15.2	15.0	89	1.0	8.10.0