What can cause a function call scheduled via setTimeout to be delayed differently from the set time?

A function call via setTimeout can be delayed from the set time for several reasons:

1. Single-threaded nature and event loop of Node.js: Node.js operates on a single thread, and if the main thread is busy executing other code (for example, a heavy synchronous operation) when the timer triggers, the execution of the delayed function will be delayed.

2. Minimum timer delay: In some environments, there is a minimum delay value (for example, 1 ms or 4 ms), and if a smaller delay is specified, it will be rounded.

3. Delays in the event scheduler: Timers do not guarantee exact trigger times, only a minimum delay. If the event queue is busy, execution may be postponed.

4. System factors: CPU load, context switching, process priorities, and other system events can affect timer accuracy.

Example:

setTimeout(() => {
  console.log('Executed after delay');
}, 1000);

// If a heavy operation is running at this time, the call may occur later than 1000 ms