Async JavaScript

Timers, Scheduling & Debouncing

Timers schedule future tasks, but they are not precise clocks. Debouncing and throttling shape frequent events so expensive work runs at a controlled rate.

Timer delay is a minimum, not a guarantee
Debounce waits for quiet
Throttle enforces a maximum rate
Intervals can overlap conceptually
Fake timers make time testable

Scheduling patterns
Pattern	Behavior	Best for
setTimeout	Run once after delay	Timeouts, delayed work
setInterval	Run repeatedly	Simple polling
Debounce	Run after quiet period	Search input
Throttle	Run at most every N ms	Scroll/drag events
requestAnimationFrame	Before browser paint	Visual updates

Debounce

function debounce(fn, delay) {
  let id
  return (...args) => {
    clearTimeout(id)
    id = setTimeout(() => fn(...args), delay)
  }
}

const search = debounce((query) => fetchResults(query), 300)

Every call resets the timer; only the final quiet-period call runs.