Debounce Enhanced

mediumcodingJavaScriptFunctionsTiming~25 min

Asked at Meta, Vercel, Stripe

Overview

Implement debounce(fn, delay) that returns a debounced function with .cancel() and .flush() methods.

.cancel() — cancels pending invocation
.flush() — immediately invokes pending invocation

Examples

const d = debounce(fn, 100);
d('a'); d('b');
d.flush(); // immediately calls fn('b')

Solution

Reveal solution

function debounce(fn, delay) {
  let timer = null;
  let lastArgs = null;
  let lastThis = null;
  function debounced(...args) {
    lastArgs = args;
    lastThis = this;
    if (timer) clearTimeout(timer);
    timer = setTimeout(() => { fn.apply(lastThis, lastArgs); timer = null; lastArgs = null; }, delay);
  }
  debounced.cancel = () => { if (timer) { clearTimeout(timer); timer = null; lastArgs = null; } };
  debounced.flush = () => { if (timer) { clearTimeout(timer); timer = null; fn.apply(lastThis, lastArgs); lastArgs = null; } };
  return debounced;
}

debounce-enhanced.js

Debounce Enhanced

mediumcodingJavaScriptFunctions

Overview

Implement debounce(fn, delay) that returns a debounced function with .cancel() and .flush() methods.

.cancel() — cancels pending invocation
.flush() — immediately invokes pending invocation

Examples

const d = debounce(fn, 100);
d('a'); d('b');
d.flush(); // immediately calls fn('b')

Solution

Reveal solution

function debounce(fn, delay) {
  let timer = null;
  let lastArgs = null;
  let lastThis = null;
  function debounced(...args) {
    lastArgs = args;
    lastThis = this;
    if (timer) clearTimeout(timer);
    timer = setTimeout(() => { fn.apply(lastThis, lastArgs); timer = null; lastArgs = null; }, delay);
  }
  debounced.cancel = () => { if (timer) { clearTimeout(timer); timer = null; lastArgs = null; } };
  debounced.flush = () => { if (timer) { clearTimeout(timer); timer = null; fn.apply(lastThis, lastArgs); lastArgs = null; } };
  return debounced;
}

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