setTimeout(), setInterval(), and requestAnimationFrame()

const start = performance.now();
setTimeout(() => {
  const elapsed = performance.now() - start;
  console.log(elapsed);
}, 100);

performance.now() is inaccurate
setTimeout always adds random delay
Other code execution and browser activities can delay timeout execution
The logged time may exceed 100ms because: 1) setTimeout provides minimum, not exact, delay, 2) Main thread blocking can delay execution, 3) Browser throttling affects background tabs, 4) System load impacts timing accuracy, 5) Event loop may be busy with other tasks, 6) Browser's timer resolution limits precision.
The JavaScript engine is slow