W3School TIY Editor

<!DOCTYPE html>
<html>
<head>
<style>
.slideUp {
  animation-name: slideUp;
  -webkit-animation-name: slideUp;
  animation-duration: 1s;
  -webkit-animation-duration: 1s;
  visibility: visible;
}

@keyframes slideUp {
  0% {
    opacity: 0;
    -webkit-transform: translateY(70%);
  } 
  100% {
    opacity: 1;
    -webkit-transform: translateY(0%);
  }
}

@-webkit-keyframes slideUp {
  0% {
    opacity: 0;
    -webkit-transform: translateY(70%);
  } 
  100% {
    opacity: 1;
    -webkit-transform: translateY(0%);
  }
}

body {height:1500px;}
.col-1 {float:left}
.col-2 {float:left;padding-left:25px;}
img {width:180px;height:100px;visibility:hidden;}
hr {margin-top:400px;}
</style>
</head>
<body>

<p>请向下滚动此页面</p>
<p>当您从顶部滚动 350 像素时，图像将滑入。</p>

function myFunction() {
  if (document.body.scrollTop > 350 || document.documentElement.scrollTop > 350) {
    document.getElementById("myImg").className = "slideUp";
  }
}
</script>

</body>
</html>