The Meta Frontend Loop Questions (2024)
Four utility-belt questions from a frontend loop at a large social platform in early 2024. They look like trivia but each one is graded on a specific edge case. Mine got me to round three.
Question Bundle
JavaScript
interview-prep
frontend
meta
By @davidmorgan
December 16, 2025
·
Updated August 9, 2026
1,173 views
23
4.5 (10)
Implement a debounce(fn, wait) utility. Calling the returned function repeatedly should only invoke fn once, wait ms after the last call. Bonus: support cancel().
On the whiteboard
On the whiteboard I'd write:
JavaScript
const d = debounce(save, 300);
d('a'); d('ab'); d('abc'); // three calls inside 300ms
// 300ms after the last call: save('abc') fires once with the trailing args
d.cancel(); // before the timer fires, drops the queued invocation3 more questions and all solutions are locked.
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