test.html

<!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>Document</title>
    <style>
      .father {
        height: 400px;
        background-color: skyblue;
        overflow: hidden;
      }
      .son {
        height: 800px;
        background-color: black;
      }
    </style>
  </head>
  <body>
    <div class="father">
      <div class="son"></div>
    </div>
  </body>
  <script src="https://unpkg.com/@better-scroll/core@latest/dist/core.js"></script>
  <script>
    let wrapper = document.querySelector(".father");
    let bs = new BScroll(wrapper, {
      mouseWheel: true,
      scrollbar:true
    });
    console.log(bs)
  </script>
</html>