js控制多个滚动条联动显示，以及解决滑动鼠标滚轮导致的问题

参考文章 原生JS控制多个滚动条同步跟随滚动

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>滚动条联动</title>
  <style>
    .div1,
    .div2 {
      width: 200px;
      height: 300px;
      float: left;
      overflow: auto;
    }

    .div2 {
      margin-left: 100px;
    }

    .div3 {
      height: 800px;
      background-color: red;
    }

    .div4 {
      height: 800px;
      background-color: blue;
    }
  </style>
</head>

<body>
  <div class="div1">
    <div class="div3"></div>
  </div>
  <div class="div2">
    <div class="div4"></div>
  </div>
</body>

<script>
  let a = document.querySelector('.div1');
  let b = document.querySelector('.div2');
  let overElement = '';

  a.onmouseover = () => {
    overElement = 'a';
  }
  b.onmouseover = () => {
    overElement = 'b';
  }

  a.addEventListener('scroll', () => {
    if (overElement === 'a') {
      b.scrollTop = a.scrollTop;
    }
  });
  b.addEventListener('scroll', () => {
    if (overElement === 'b') {
      a.scrollTop = b.scrollTop;
    }
  });
</script>

</html>