The Atomics.notify() static method notifies up some agents that are sleeping in the wait queue.

Note: This operation works with a shared Int32Array only. It will return 0 on non-shared ArrayBuffer objects.


Atomics.notify(typedArray, index, count)



A shared Int32Array.


The position in the typedArray to wake up on.

count Optional

The number of sleeping agents to notify. Defaults to +Infinity.

Return value

  • Returns the number of woken up agents.
  • Returns 0, if a non-shared ArrayBuffer object is used.



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 which is expected to be 0. As long as that is true, it will not go on. However, once the writing thread has stored a new value, it will be notified by the writing thread and return the new value (123).

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;, 0, 123);
Atomics.notify(int32, 0, 1);


ECMAScript Language Specification
# sec-atomics.notify

Browser compatibility

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See also