JavaScript实现Div折叠展开效果及定时器机制解析

核心代码与HTML结构

<script type="text/javascript" language="javascript">
  function $(obj)
  {
  return document.getElementById(obj);
  }
  function ToggleDiv()
  {
  this.ToggleId='silder'; //被伸缩的对象ID
  this.ParentId='container'; //被伸缩的对象的父ID
  this.minHeight=1; //最小高度
  this.maxHeight=200; //最大高度
  this.speed=1; //伸缩速度
  this.offset=0.15; //偏移量
  this.load=function()
  {
   if($(this.ToggleId).style.display=='none') //如果是隐藏的就打开
   {
    StartToggle('open',this.ToggleId,this.ParentId,this.minHeight,this.maxHeight,this.speed,this.offset);
   }
   else //如果是打开的就隐藏
   {
     StartToggle('close',this.ToggleId,this.ParentId,this.minHeight,this.maxHeight,this.speed,this.offset);
   }
  }
  }
  function StartToggle(method,toggleid,parentid,minheight,maxheight,speed,offset)
  {
  if(typeof(method)!='string' || method.toLowerCase()=='')
  {
   method='open';
  }
  if(method.toLowerCase()=='open')
  {
   var addspeed=speed+offset;
   var openfun=function()
   {
    var originheight=$(toggleid).offsetHeight==0?1:$(toggleid).offsetHeight;
    var newheight=originheight+addspeed;
    addspeed=addspeed+offset;
    if(parseInt(newheight)<parseInt(maxheight))
    {    
     $(toggleid).style.height=newheight+'px';
     $(toggleid).style.display='block';
    }
    else if(parseInt(newheight)>=parseInt(maxheight))
    {
     $(toggleid).style.height=maxheight+'px';
     $(toggleid).style.display='block';
     $(parentid).innerHTML='收缩';
     window.clearInterval(addtimer);
    }
   }
   var addtimer=window.setInterval(openfun,100);
  }
  else if(method.toLowerCase()=='close')
  {
   var addspeed=speed+offset;
   var reducefunction=function()
   {
    var originheight=$(toggleid).offsetHeight;
    var newheight=originheight-addspeed;
    addspeed=addspeed+offset;
    if(parseInt(newheight)>parseInt(minheight))
    {
     $(toggleid).style.height=newheight+'px';
     $(toggleid).style.display='block';
    }
    else
    {
     $(toggleid).style.display='none';
     $(toggleid).style.height='1px';
     $(parentid).innerHTML='展开';
     window.clearInterval(reducetimer);
    }
   }
   var reducetimer=window.setInterval(reducefunction,100);
  }
  }
  function DoToggle(obj1,obj2)
  {
  var tog=new ToggleDiv();
  tog.ToggleId=obj1;
  tog.ParentId=obj2;
  tog.minHeight=5;
  tog.maxHeight=110;
  tog.speed=10;
  tog.offset=3;
  tog.load();
  }
</script>

<div style="border:1px dashed blue;width:200px;">
  <h2 id="container" onclick="javascript:DoToggle('silder',this.id);" onmouseover="this.style.cursor='pointer';">展开</h2>
  <div id="silder" style="display:none">
  伸缩效果<br />
  伸缩效果<br />
  伸缩效果<br />
  伸缩效果<br />伸缩效果<br />
  伸缩效果<br />
  </div>
</div>

function a()
{
 setTimeout(function(){alert('1');},0);
 alert('2');
}