Atomics.or()

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.or() static method computes a bitwise OR with 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

js
Atomics.or(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 compute the bitwise OR.

value

The number to compute the bitwise OR with.

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.

Description

The bitwise OR operation yields 1, if either a or b are 1. The truth table for the OR operation is:

a b a | b
0 0 0
0 1 1
1 0 1
1 1 1

For example, a bitwise OR of 5 | 1 results in 0101 which is 5 in decimal. 

5  0101
1  0001
   ----
5  0101

Examples

Using or

js
const sab = new SharedArrayBuffer(1024);
const ta = new Uint8Array(sab);
ta[0] = 2;

Atomics.or(ta, 0, 1); // returns 2, the old value
Atomics.load(ta, 0); // 3

Specifications

Specification
ECMAScript Language Specification
# sec-atomics.or

Browser compatibility

BCD tables only load in the browser

See also