JS實(shí)現(xiàn)長(zhǎng)圖上下滾動(dòng)效果

<div id="box">
 <img id="pic" src="./program1/images/1.jpg" alt="">
 <div id="top"></div>
<div id="bottom"></div>

//通用樣式
 * {
 margin: 0;
 padding: 0;
 }
 #box {
 width: 750px;
 height: 200px;
 border: 1px solid #000;
 margin: 200px auto;
 overflow: hidden; /*圖片溢出部分隱藏*/
 position: relative; /*子絕父相*/
 }

 #pic {
 position: absolute;
 left: 0;
 right: 0;
 }

 
 #top {
 width: 100%;
 height: 50%;
 position: absolute; /*子絕父相*/
 left: 0;
 cursor: pointer; /*鼠標(biāo)*/
  /* 頂部對(duì)齊 */
 top:0; 
 }
 
 #bottom {
 width: 100%;
 height: 50%;
 position: absolute; /*子絕父相*/
 left: 0;
 cursor: pointer;
 /* 底部對(duì)齊 */
 bottom: 0;
 }
</style>

 top.onmouseover = function(){
  // 改變pic中的top 
  // 清除定時(shí)器
  // alert(0);
  clearInterval(intervalId);

  // 設(shè)置定時(shí)器 
  intervalId = setInterval(function(){
  if(num > -600){
   num -= 10;
   pic.style.top = num + "px";
  }
  
  },20);

top.onmouseout = function() {
  clearInterval(intervalId);
 }

<script>
 window.onload = function() {
 // 獲取標(biāo)簽
 var box = document.getElementById('box');
 var pic = document.getElementById('pic');
 var top = document.getElementById('top');
 var bottom = document.getElementById('bottom');
 var intervalId, num = 0;
 // 鼠標(biāo)進(jìn)入上半部分
 top.onmouseover = function(){
  // 改變pic中的top 
  // 清除定時(shí)器
  // alert(0);
  clearInterval(intervalId);

  // 設(shè)置定時(shí)器
  intervalId = setInterval(function(){
  if(num > -600){
   num -= 10;
   pic.style.top = num + "px";
  }
  
  },20);

 };
  // 鼠標(biāo)移出上半部分
 top.onmouseout = function() {
  clearInterval(intervalId);
 }
 // 鼠標(biāo)進(jìn)入下半部分
 bottom.onmouseover = function(){
  // 改變pic中的top 
  // 清除定時(shí)器
  // alert(0);
  clearInterval(intervalId);

  // 設(shè)置定時(shí)器
  intervalId = setInterval(function(){
  if(num < 0){
   num += 10;
   pic.style.top = num + "px";
  }
  
  },20);
 };
 // 鼠標(biāo)移出下半部分
 bottom.onmouseout = function() {
  clearInterval(intervalId);
 };
 
 }
</script>