throttle.js

// wait in milliseconds
function throttle(fn, wait) {
  // unix timestamp
  let lastTimeExecuted;

  return function (args) {
    const currentTime = new Date();

    // this condition is satisfied only the very first time
    if (!lastTimeExecuted) {
      lastTimeExecuted = currentTime;
      fn(args);
      return;
    }

    // we already have some date in lastTimeExecuted, so we calculate
    // diff in milliseconds
    const msPassed = currentTime.getTime() - lastTimeExecuted.getTime();

    // save it for feature runs
    lastTimeExecuted = currentTime;

    // runs original function only if `wait` time passed
    if (msPassed > wait) fn(args)
  }
}