tweenmax 使用

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
        content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style type="text/css">
    * {
      margin: 0;
      padding: 0;
    }
    /*第一种实现方法*/

    /* main {
         min-height: calc(100vh - 2.9em - 8em);
         box-sizing: border-box;
     }
     footer {
         background: #000;
         color: #fff;
     }*/
    /*第二种实现方法*/
    body {
      display: flex;
      flex-flow: column;
      min-height: 100vh;
    }
    main {
      flex: 1;
      position: relative;

    }
    main p {
      margin: 50vh auto 0 auto;
      transform: translateY(-50%);
      background-size: 100%;
      width: 400px;
      height: 250px;
      overflow: auto;
      opacity: 0;
      background: red;
    }
    footer {
      background: #000;
      color: #fff;


    }
    li:nth-child(3n+4) {
      background: pink;
    }
    .animated {
      opacity: 1;
    }
  </style>


</head>
<body>
<header>
  <h1>site name</h1>
</header>
<main>
  <p class="twee  twee1">

  </p>
  <p class="twee twee2">


  <p class="twee twee3">
    
  </p>


</main>


<footer>
  <p>© 2015 No rights reserved.</p>
  <p>Made with ♥ by an anonymous pastafarian.著作权归作者所有。
  </p>
</footer>

<script charset="utf-8" src="https://nie.res.netease.com/comm/js/jquery(mixNIE).1.11.js"></script>
<script src="https://nie.res.netease.com/comm/js/nie/ref/??tweenmax.js"></script>
<script>
  (function() {
    function kv (index) {
      let _key = `.twee${index+1}`
      let teww=TweenMax.fromTo(_key, 2,{ opacity: 0, x: 800, y: 120, z: 200, rotationZ: -320, scaleX: 1.2, scaleY: 1.2 },
        { opacity: 1, x: 0, y: 0, z: 0, rotationZ: 0, scaleX: 1, scaleY: 1 ,ease: Power2.easeOut,onComplete() {
          }})
    }
    const throttle = function (func, wait, mustRun) {
      let timeout
      let startTime = new Date()
      return function () {
        let context = this
        let args = arguments
        let curTime = new Date()
        clearTimeout(timeout)
        // 如果达到了规定的触发时间间隔，触发 handler
        if (curTime - startTime >= mustRun) {
          func.apply(context, args)
          startTime = curTime
          // 没达到触发间隔，重新设定定时器
        } else {
          timeout = setTimeout(func, wait)
        }
      }
    }

    let elements = Array.prototype.slice.call($('.twee'));
    let windowHeight = $(window).height();
    let offsetArr = [];
    let scrollTop = 0;
    let reqId = null;
    let lastFinish = false;
    elements.forEach((item,index)=> {
      let _item = $(item);
      let offset = 0;
      let diff = Math.ceil(_item.offset().top-windowHeight*3/4);
      diff > 0 ? (offset=diff) : (offset=0);
      offsetArr.push(offset);
    })
    $(window).on('scroll', throttle(function () {
      scrollTop = $(this).scrollTop()
      console.log(scrollTop)
    }, 400, 500))
    step();
    function step() {
      if (lastFinish) return false;
      for(let i =0; i<elements.length; i++){
        /*console.log(offsetArr)
        console.log(scrollTop, offsetArr[i]-10)*/
        if(scrollTop>=offsetArr[i]-10){
          doAnimate(i)
        }

      }

      reqId = requestAnimationFrame(step)
    }
    function doAnimate(index) {
      console.log(index)
      if($(elements[index]).hasClass('animated')) return false;
      $(elements[index]).addClass('animated');
      if(index<offsetArr.length-1) {
        kv(index)
      }else if(index>=offsetArr.length-1) {
        setTimeout(function() {
          cancelAnimationFrame(reqId);
          reqId = null;
          lastFinish = true;
        },2500)
      }


    }
  })()
</script>
</body>
</html>