Atomics.wait()

The Atomics.wait() static method verifies that a shared memory location still contains a given value and if so sleeps, awaiting a wake-up notification or times out. It returns a string which is either "ok", "not-equal", or "timed-out".

Note: This operation only works with an Int32Array or BigInt64Array that views a SharedArrayBuffer, and may not be allowed on the main thread. For a non-blocking, asynchronous version of this method, see Atomics.waitAsync().

Syntax

js
Atomics.wait(typedArray, index, value)
Atomics.wait(typedArray, index, value, timeout)

Parameters

typedArray

An Int32Array or BigInt64Array that views a SharedArrayBuffer.

index

The position in the typedArray to wait on.

value

The expected value to test.

timeout Optional

Time to wait in milliseconds. NaN (and values that get converted to NaN, such as undefined) becomes Infinity. Negative values become 0.

Return value

A string which is either "ok", "not-equal", or "timed-out".

Exceptions

TypeError

Thrown in one of the following cases:

RangeError

Thrown if index is out of bounds in the typedArray.

Examples

Using wait()

Given a shared Int32Array:

js
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).

js
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:

js
console.log(int32[0]); // 0;
Atomics.store(int32, 0, 123);
Atomics.notify(int32, 0, 1);

Specifications

Specification
ECMAScript Language Specification
# sec-atomics.wait

Browser compatibility

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See also