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How setTimeout and setInterval Work in JavaScript
- Timers in JavaScript, such as setTimeout and setInterval, are managed by the environment around JavaScript, not the engine itself.
- When setTimeout is called, the function won't necessarily run exactly after the specified time but after it, depending on other tasks.
- setInterval sets up a repeating schedule, adding functions to the task queue each time the timer fires.
- If JavaScript is busy when setInterval fires again, the new task has to wait its turn, making it a reminder rather than immediate execution.
- The passed delay in setTimeout and setInterval is a minimum; the function may run later due to timer scheduling and JavaScript's workload.
- JavaScript adds timer functions to a queue of tasks which are executed when the current stack is empty.
- Long-running synchronous code can delay timer callbacks as JavaScript completes the current tasks before moving to queued tasks.
- setInterval may cause delays and skipped intervals if callbacks take too long, affecting the desired timing.
- Modern browsers throttle timers in background tabs to save resources, potentially affecting the precision and consistency of timer execution.
- The event loop controls when timer callbacks run, ensuring tasks are executed in the order they were added, based on JavaScript's workload.
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