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JavaScript·Intermediate·Coding·1 min read

How do debounce and throttle differ?

Short interview answer

Debounce waits for a quiet period before invoking, so a burst collapses into one call. Throttle limits invocation to at most once per interval while activity continues. Search suggestions often debounce; continuous scroll measurement may throttle or align work to animation frames.

Example

JavaScript
function debounce(fn, delay) {  let t;  return (...args) => {    clearTimeout(t);    t = setTimeout(() => fn(...args), delay); // fires only after calls stop  };}
function throttle(fn, interval) {  let last = 0;  return (...args) => {    const now = Date.now();    if (now - last >= interval) { last = now; fn(...args); } // at most 1/interval  };}

Key takeaway

Explain the underlying mental model clearly, then support it with a concrete example and its trade-offs.

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