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

Note: This operation works with a shared Int32Array only.


Atomics.wake(typedArray, index, count)


A shared Int32Array.
The position in the typedArray to wake up on.
The number of sleeping agents to wake. Defaults to +Infinity.

Return value

A number of woken up agents.



Given a shared Int32Array:

var sab = new SharedArrayBuffer(1024);
var 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 woken up 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 wakes up the waiting thread once it has written:

console.log(int32[0]); // 0;, 0, 123); 
Atomics.wake(int32, 0, 1);


Specification Status Comment
ECMAScript Latest Draft (ECMA-262)
The definition of 'Atomics.wake' in that specification.
Draft Initial definition in ES2017.

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support No support [2] [4] No support 55 (55) [1] [3] No support No support No support
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support No support 55.0 (55) [1] No support No support No support

[1] In Firefox version 46 until version 54, this feature is disabled by a preference setting. In about:config, set javascript.options.shared_memory to true

[2] The implementation is under development and needs these runtime flags: --js-flags=--harmony-sharedarraybuffer --enable-blink-feature=SharedArrayBuffer

[3] In versions 46 and 47, this method was named Atomics.futexWake() and the count parameter defaulted to 0.

[4] The count parameter defaults to 0, instead of +Infinity.

See also

Document Tags and Contributors

 Contributors to this page: fscholz, btzy
 Last updated by: fscholz,