How does setTimeout work behind the scenes in JavaScript?
It hands the timer to a Web API, continues running synchronous code, and when the timer fires, pushes the callback to the macrotask queue. The event loop runs the callback only when the call stack is empty and microtasks are done.
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More FAQs in How setTimeout Works Behind the Scenes in JavaScript
No. The callback goes to the macrotask queue. The event loop runs it only after the current call stack is empty and all microtasks are done. So it runs after synchronous code.
Because promise callbacks go to the microtask queue, which the event loop drains completely before touching the macrotask queue where setTimeout callbacks live. Microtasks always run before macrotasks.
No. It guarantees a minimum delay, not an exact delay. The actual delay depends on the call stack, the microtask queue, timer throttling in background tabs, and nested timer throttling.
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