A technique that delays function execution until the user stops calling it for a specified delay. Each call clears the previous timer and sets a new one. Only the last call executes.

function debounce(fn, delay) { let timer; return function(...args) { clearTimeout(timer); timer = setTimeout(() => fn.apply(this, args), delay); }; }

To avoid making an API call on every keystroke. Without debounce, typing 'hello' makes 5 calls. With debounce (300ms), only 1 call is made after the user stops typing.