Atomics.or()

BaselineWidely available

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

TheAtomics.or() staticmethod computes a bitwise OR with a given value at a given position in the array, andreturns the old value at that position. This atomic operation guarantees that no otherwrite happens until the modified value is written back.

Try it

// Create a SharedArrayBuffer with a size in bytesconst buffer = new SharedArrayBuffer(16);const uint8 = new Uint8Array(buffer);uint8[0] = 5;// 5 (0101) OR 2 (0010) = 7 (0111)console.log(Atomics.or(uint8, 0, 2));// Expected output: 5console.log(Atomics.load(uint8, 0));// Expected output: 7

Syntax

Atomics.or(typedArray, index, value)

Parameters

typedArray: An integer typed array. One ofInt8Array,Uint8Array,Int16Array,Uint16Array,Int32Array,Uint32Array,BigInt64Array, orBigUint64Array.
index: The position in thetypedArray 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 iftypedArray is not one of the allowed integer types.
RangeError: Thrown ifindex is out of bounds in thetypedArray.

Description

The bitwise OR operation yields 1, if eithera orb 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 of5 | 1 results in0101 which is 5in decimal.

5  01011  0001   ----5  0101

Examples

Using or

const sab = new SharedArrayBuffer(1024);const ta = new Uint8Array(sab);ta[0] = 2;Atomics.or(ta, 0, 1); // returns 2, the old valueAtomics.load(ta, 0); // 3