JS优化常用片断

function debounce(func, delay) {
  let isCooldown = false;
  return function() {
    if (isCooldown) return;
    func.apply(this, arguments);
    isCooldown = true;
    setTimeout(() => isCooldown = false, delay);
  };
}

function throttle(func, delay) {

  let isThrottled = false,
    savedArgs,
    savedThis;

  function wrapper() {

    if (isThrottled) { // (2)
      savedArgs = arguments;
      savedThis = this;
      return;
    }

    func.apply(this, arguments); // (1)

    isThrottled = true;

    setTimeout(function() {
      isThrottled = false; // (3)
      if (savedArgs) {
        wrapper.apply(savedThis, savedArgs);
        savedArgs = savedThis = null;
      }
    }, delay);
  }

  return wrapper;
}