The canonical sleep wraps setTimeout in a Promise so it composes inside async functions with await. The resolver is the timeout callback, so the promise settles exactly once after ms milliseconds. Use it for retry backoffs, demo pauses, or rate-limited loops where you do not need to cancel the wait. The function is O(1) time and uses one timer slot per pending sleep, so do not spawn thousands of them in a tight loop without cleaning up.

Adding AbortSignal support turns sleep into a first-class cancellable primitive that fits the modern Web API contract. The wrapper checks for an already-aborted signal up front, registers an abort listener that clears the timer and rejects with an AbortError, and tears the listener down on natural completion to avoid leaks. Callers can chain it with fetch, axios cancel tokens, or any other abort-aware helper using a shared AbortController. This is the pattern most utility libraries (p-timeout, delay) settled on for compatibility.