Web/JavaScript/Reference/Global objects/Atomics/notify

The static Atomics.notify() 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.

Syntax

Atomics.notify(typedArray, index, count)

Parameters

typedArray

A shared Int32Array.

index

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.

Exceptions

• Throws a TypeError, if typedArray is not a Int32Array.
• Throws a RangeError, if index is out of bounds in the typedArray.

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

Specifications

Specification

ECMAScript (ECMA-262)The definition of 'Atomics.notify' in that specification.

Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
notify	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Alternate Name' Notes' Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place. Alternate Name' Uses the non-standard name: wake	Edge Full support 79	Firefox Full support 78 Full support 78 Full support 63 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 63: this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config. Full support 57 Notes' Alternate Name' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Alternate Name' Uses the non-standard name: wake Disabled' From version 57: this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 48 — 55 Disabled' Disabled' From version 48 until version 55 (exclusive): this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config. No support 46 — 48 Notes' Alternate Name' Disabled' Notes' The count parameter defaults to 0 instead of the later-specified +Infinity. Alternate Name' Uses the non-standard name: futexWake Disabled' From version 46 until version 48 (exclusive): this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1 Alternate Name' No support 10.1 — 11.1 Alternate Name' Alternate Name' Uses the non-standard name: wake	WebView Android No support 60 — 63 Notes' Alternate Name' No support 60 — 63 Notes' Alternate Name' Notes' Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place. Alternate Name' Uses the non-standard name: wake	Chrome Android No support 60 — 63 Notes' Alternate Name' No support 60 — 63 Notes' Alternate Name' Notes' Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place. Alternate Name' Uses the non-standard name: wake	Firefox Android Full support 63 Notes' Disabled' Full support 63 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 63: this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config. Full support 57 Notes' Alternate Name' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Alternate Name' Uses the non-standard name: wake Disabled' From version 57: this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 48 — 55 Disabled' Disabled' From version 48 until version 55 (exclusive): this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config. No support 46 — 48 Notes' Alternate Name' Disabled' Notes' The count parameter defaults to 0 instead of the later-specified +Infinity. Alternate Name' Uses the non-standard name: futexWake Disabled' From version 46 until version 48 (exclusive): this feature is behind the javascript.options.shared_memory preference (needs to be set to true). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' Alternate Name' No support No Notes' Alternate Name' Notes' Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place. Alternate Name' Uses the non-standard name: wake	nodejs Full support 8.10.0 Alternate Name' Full support 8.10.0 Alternate Name' Alternate Name' Uses the non-standard name: wake

Legend

Full support  

Full support

No support  

No support

See implementation notes.'

See implementation notes.

User must explicitly enable this feature.'

User must explicitly enable this feature.

Uses a non-standard name.'

Uses a non-standard name.

See also

• Atomics
• Atomics.wait()

Atomics.notify() by Mozilla Contributors is licensed under CC-BY-SA 2.5.