函数防抖

//   防抖
  function dobounce(fn, dealy) {
    let timer = null;
    return function() {
      if (timer) {
        clearTimeout(timer);/// 主要是这里清除定时器  对比节流这里是直接return
      }
      timer = setTimeout(() => {
        fn.apply(this, arguments);
        timer = null;
      }, dealy);
    };
  }
  let input1 = document.getElementById("input1");
  input1.addEventListener(
    "keyup",
    dobounce(() => {
      console.log(input1.value);
    }, 5000)
  );

  <input type="text" id="input1" />