text: //scrollBody：滚动条的整体的id,div#id；scrollBlock：滚动滑块的id,div#id；divBox:内容显示区域的id,div#id，cntList：实际内容的id,div#id;
  
  function cstumScroll(scrollBody,scrollBlock,divBox,cntList,wH=window.innerHeight){
  	
  	if($("#menu_ul").outerHeight()<$("#menu").outerHeight()){
  		$("#scroll_bar").css("display","none");
  		$("#menu_ul").css("top","0");
  	}
      const div1 = document.getElementById(scrollBody);
      const div2 = document.getElementById(scrollBlock);
      const div3 = document.getElementById(divBox);
      const txt = document.getElementById(cntList);
  //  div1.style.height= div3.style.height = wH + 'px';
      //div1.style.height = div3.style.height = box.offsetHeight + 'px';
      div2H = div1.offsetHeight*div3.offsetHeight/txt.scrollHeight;
      div2.style.height = div2H + 'px';
      if(div2H < 20){
          div2.style.height = '20px';
      }else{
          div2.style.height = div2H + 'px';
      }
      div2.onmousedown = div3.onmousedown= function(ev){
  //      console.log(ev.pageY);
          let disY = ev.pageY - div2.offsetTop;
  
  //      console.log(txt.style.height);
  
          document.onmousemove = function(ev){
              let t = ev.pageY - disY;
  
              if(t < 0){
                  t = 0;
              }else if(t > div1.clientHeight - div2.clientHeight){
                  t = div1.clientHeight - div2.clientHeight;
              }
  
              /*
                  核心就是这个比例
              */
              let scale = t /  (div1.clientHeight - div2.clientHeight);
              
              txt.style.top =  scale *  (div3.offsetHeight - txt.scrollHeight) + 'px';
              div2.style.top = t + 'px';
          }
          document.onmouseup = function(){
              document.onmousemove = document.onmouseup = null;
          }
          return false;
      }
      addWheel(div1,function(o){
          let t = div2.offsetTop;
          if(o){
              t -= 5;
          }else{
              t += 5;
          }
          if(t < 0){
              t = 0;
          }else if(t > div1.clientHeight - div2.clientHeight){
              t = div1.clientHeight - div2.clientHeight;
          }
          let scale = t /  (div1.clientHeight - div2.clientHeight);
          txt.style.top =  scale *  (div3.offsetHeight - txt.scrollHeight) + 'px';
          div2.style.top = t + 'px';
      });
  
  
      function addWheel(obj,fn){
          obj.addEventListener('mousewheel',callback);
          obj.addEventListener('DOMMouseScroll',callback);
  
          function callback(ev){
              let o = true; //向上
              if(ev.wheelDelta){
                  o = ev.wheelDelta > 0?true:false;
              }else{
                  o = ev.detail < 0? true:false;
              }
              fn && fn(o);
              ev.preventDefault();
          }
      }
  }
  
  