What are Web APIs in JavaScript async handling?
Browser-provided async operations: setTimeout, fetch, DOM events, geolocation, etc. They run outside the JS engine. When the operation completes, the callback is pushed to the microtask or macrotask queue for the event loop to pick up.
Verify This Answer
Cross-check this information using these trusted sources:
More FAQs in How JavaScript Handles Asynchronous Operations
Through the runtime environment. Web APIs (browser) or libuv (Node.js) handle async operations outside the engine. When done, callbacks go to queues. The event loop moves callbacks to the call stack when it is empty. The engine itself stays synchronous.
Synchronous at the language level (one call stack, one statement at a time). The runtime (Web APIs, queues, event loop) provides asynchronous behavior. The engine itself never runs two things at once.
It hands the timer to a Web API, continues running synchronous code, and when the timer fires the callback is pushed to the macrotask queue. The event loop runs the callback only when the call stack is empty and microtasks are done.
Still have questions?
Browse all our FAQs or reach out to our support team