Atomics.notify()
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.notify() static
method notifies up some agents that are sleeping in the wait queue.
Note:
This operation only works with an Int32Array or BigInt64Array that views a SharedArrayBuffer.
It will return 0 on non-shared ArrayBuffer objects.
Syntax
Atomics.notify(typedArray, index, count)
Parameters
typedArray-
An
Int32ArrayorBigInt64Arraythat views aSharedArrayBuffer. index-
The position in the
typedArrayto wake up on. countOptional-
The number of sleeping agents to notify. Defaults to
Infinity.
Return value
Returns the number of woken up agents, or 0 if typedArray is a view on a non-shared ArrayBuffer.
Exceptions
TypeError-
Thrown if
typedArrayis not anInt32ArrayorBigInt64Array. RangeError-
Thrown if
indexis out of bounds in thetypedArray.
Examples
Using notify
Given a shared Int32Array:
const sab = new SharedArrayBuffer(1024);
const int32 = new Int32Array(sab);
A reading thread is sleeping and waiting on location 0 because the provided value matches what is stored at the provided index.
The reading thread will not move on until the writing thread has called Atomics.notify() on position 0 of the provided typedArray.
Note that if, after being woken up, the value of location 0 has not been changed by the writing thread, the reading thread will not go back to sleep, but will continue on.
Atomics.wait(int32, 0, 0);
console.log(int32[0]); // 123
A writing thread stores a new value and notifies the waiting thread once it has written:
console.log(int32[0]); // 0;
Atomics.store(int32, 0, 123);
Atomics.notify(int32, 0, 1);
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-atomics.notify |
Browser compatibility
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