防抖与节流实现

function debounce(fn, delay = 300) {
  //默认300毫秒
  let timer;
  return function () {
    const args = arguments;
    if (timer) {
      clearTimeout(timer);
    }
    timer = setTimeout(() => {
      fn.apply(this, args); // 改变this指向为调用debounce所指的对象
    }, delay);
  };
}    
// 测试
window.addEventListener(
  "scroll",
  debounce(() => {
    console.log(111);
  }, 1000)
);

// 节流
// 设置一个标志
function throttle(fn, delay) {
  let flag = true;
  return () => {
    if (!flag) return;
    flag = false;
    timer = setTimeout(() => {
      fn();
      flag = true;
    }, delay);
  };
}

window.addEventListener(
  "scroll",
  throttle(() => {
    console.log(111);
  }, 1000)
);