// 防抖 规定时间内持续触发只执行最后一次操作
function debounce(fn, delay) {
  let timer = null;
  return function () {
    if (timer) clearTimeout(timer);
    timer = setTimeout(() => {
      fn.apply(this, arguments)
    }, delay)
  }
}

// 节流 规定时间内持续触发只执行第一次操作
function throttle(fn, delay) {
  let beginTime = 0;
  return function () {
    const triggle = new Date().getTime();
    if (triggle - beginTime > delay) {
      fn.apply(this, arguments);
      beginTime = triggle;
    }
  }
}