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

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

  • : 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:
    • If typedArray is not an Int32Array or BigInt64Array that views a SharedArrayBuffer.
    • If the current thread cannot be blocked (for example, because it's the main thread).
• RangeError
  • : Thrown if index is out of bounds in the typedArray.

Examples

Using wait()

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

Browser compatibility

See also

• Atomics
• Atomics.waitAsync
• Atomics.notify