Implement debounce, then make it cancellable

Easy20 minFree, no account

The classic warm-up, and the follow-up that catches people who learned it by heart.

The question

Write debounce(fn, wait): the returned function delays calling fn until wait milliseconds have passed without another call.

Then add .cancel() to drop a pending call, and .flush() to run it immediately.

function debounce(fn, wait) {
  // returns a function with .cancel() and .flush()
}

const save = debounce(write, 300);
save(1); save(2); save(3);   // write(3) runs once, 300ms after the last call

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The worked solution

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Score yourself

0 of 4 marked

Working debounce with correct timer reset30
cancel and flush behave correctly, including flush with nothing pending30
Preserved this and arguments, and said why25
Stated complexity and named the leading-edge or throttle variant15

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