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javascript scroll wheel control simulated scroll bar

高洛峰Original: 2016-12-09 15:55:06984browse

This example monitors the wheel event and uses the wheel to control the up and down movement of the scroll bar. It can be modified to use special effects such as zooming the picture and changing transparency using the wheel.

<!DOCTYPE html> 
<html> 
 <head> 
  <meta charset="UTF-8"> 
  <title></title> 
  <style type="text/css"> 
   *{ 
    margin: 0; 
    padding: 0; 
   } 
   #boxwrap{ 
    position: relative; 
    width: 15px; 
    height: 500px; 
    margin: 50px auto; 
    box-sizing: border-box; 
    border: 1px solid gainsboro; 
    border-radius: 6px; 
   } 
   #box{ 
    position: absolute; 
    left: 0px; 
    top: 0px; 
    width: 13px; 
    height: 30px; 
    background: gray; 
    border-radius: 6px; 
   } 
  </style> 
  <script type="text/javascript"> 
   window.onload = function (){ 
    var boxwrp = document.getElementById(&#39;boxwrap&#39;); 
    var box = document.getElementById(&#39;box&#39;); 
    //兼容firefox 
    if(boxwrp.addEventListener){ 
     document.addEventListener("DOMMouseScroll", fn, false); 
    } 
    document.onmousewheel = fn;//兼容IE、chrome 
      
    function fn(ev){ 
     var ev = ev||event; 
     var bool = false; 
     //IE、chrome 向上：120，向下：-120 
     if(ev.wheelDelta){ 
      bool= ev.wheelDelta > 0? true : false; 
     } 
     //firefox 向上：-3，向下：3 
     else{ 
      bool= ev.detail < 0? true : false; 
     } 
       
     if(bool){ 
      if(box.offsetTop>=10){ 
       box.style.top = box.offsetTop - 10 + "px"; 
      } 
      else{ 
       box.style.top = 0; 
      } 
        
     } 
     else{ 
      if(box.offsetTop<=boxwrp.offsetHeight-box.offsetHeight-10){ 
       box.style.top = box.offsetTop + 10 + "px"; 
      } 
      else{ 
       box.style.top = boxwrp.offsetHeight - box.offsetHeight + "px"; 
      } 
     } 
    } 
   } 
  </script> 
 </head> 
 <body> 
  <div id="boxwrap"> 
   <div id="box"></div> 
  </div> 
 </body> 
</html>

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