Atomics.notify()

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

[!NOTE] This operation only works with an {{jsxref("Int32Array")}} or {{jsxref("BigInt64Array")}} that views a {{jsxref("SharedArrayBuffer")}}. It will return 0 on non-shared ArrayBuffer objects.

Syntax#

Atomics.notify(typedArray, index, count)

Parameters#

• typedArray
• : An {{jsxref("Int32Array")}} or {{jsxref("BigInt64Array")}} that views a {{jsxref("SharedArrayBuffer")}}.
• index
• : The position in the typedArray to wake up on.
• count {{optional_inline}}
• : The number of sleeping agents to notify. Defaults to {{jsxref("Infinity")}}.

Return value#

Returns the number of woken up agents, or 0 if typedArray is a view on a non-shared {{jsxref("ArrayBuffer")}}.

Exceptions#

• {{jsxref("TypeError")}}
• : Thrown if typedArray is not an {{jsxref("Int32Array")}} or {{jsxref("BigInt64Array")}}.
• {{jsxref("RangeError")}}
• : Thrown if index is out of bounds in the typedArray.

Examples#

Note that these examples cannot be run directly from the console or an arbitrary web page, because SharedArrayBuffer is not defined unless its security requirements are met.

Using Atomics.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#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• {{jsxref("Atomics")}}
• {{jsxref("Atomics.wait()")}}
• {{jsxref("Atomics.waitAsync()")}}