JavaScriptintermediate

Implement throttle

Write throttle(fn, wait) that returns a throttled version of fn which runs at most once every wait ms:

the first call runs fn immediately (the leading call)
calls made during the wait are held back; when the wait ends, fn runs once more with the latest arguments and this (the trailing call)
a trailing call starts a new wait of its own, so fn never runs twice within wait ms
if a whole wait passes without any calls, the throttle resets and the next call runs immediately again

Example with wait = 100: t(1) at 0ms runs fn(1) right away; t(2) at 20ms and t(3) at 50ms are held back; at 100ms fn(3) runs, and fn(2) is never called.

Define throttle in the editor. 7 tests will call it.

one clean solution

function throttle(fn, wait) {
  let timer = null;
  let pendingArgs = null;
  let pendingThis = null;

  function startWait() {
    timer = setTimeout(() => {
      if (pendingArgs) {
        fn.apply(pendingThis, pendingArgs);
        pendingArgs = pendingThis = null;
        startWait(); // the trailing call opens a new window
      } else {
        timer = null;
      }
    }, wait);
  }

  return function throttled(...args) {
    if (timer === null) {
      fn.apply(this, args);
      startWait();
    } else {
      pendingArgs = args;
      pendingThis = this;
    }
  };
}

read the related note →

function throttle(fn, wait) { // Call fn right away on the first call, then at most once per `wait` ms. // Calls made while waiting should lead to one trailing call // with the latest arguments when the wait is over. }

Implement throttle

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