js 鼠标拖动对象 可让任何div实现拖动效果

js鼠标拖动对象：

//定义鼠标拖动对象 
drag=function (a,o){ 
     var d=document;if(!a)a=window.event; 
        if(!a.pageX)a.pageX=a.clientX; 
        if(!a.pageY)a.pageY=a.clientY; 
     var x=a.pageX,y=a.pageY; 
     if(o.setCapture) 
         o.setCapture(); 
     else if(window.captureEvents) 
         window.captureEvents(Event.MOUSEMOVE|Event.MOUSEUP); 
     var backData = {x : o.style.top, y : o.style.left}; 
     d.onmousemove=function(a){ 
         if(!a)a=window.event; 
         if(!a.pageX)a.pageX=a.clientX; 
         if(!a.pageY)a.pageY=a.clientY; 
         var tx=a.pageX-x+parseInt(o.style.left),ty=a.pageY-y+parseInt(o.style.top); 
         o.style.left=tx+"px"; 
         o.style.top=ty+"px"; 
            x=a.pageX; 
            y=a.pageY; 
     }; 
     d.onmouseup=function(a){ 
         if(!a)a=window.event; 
         if(o.releaseCapture) 
             o.releaseCapture(); 
         else if(window.captureEvents) 
             window.captureEvents(Event.MOUSEMOVE|Event.MOUSEUP); 
         d.onmousemove=null; 
         d.onmouseup=null; 
         if(!a.pageX)a.pageX=a.clientX; 
         if(!a.pageY)a.pageY=a.clientY; 
         if(!document.body.pageWidth)document.body.pageWidth=document.body.clientWidth; 
         if(!document.body.pageHeight)document.body.pageHeight=document.body.clientHeight; 
         if(a.pageX < 1 || a.pageY < 1 || a.pageX > document.body.pageWidth || a.pageY > document.body.pageHeight){ 
             o.style.left = backData.y; 
             o.style.top = backData.x; 
         } 
     }; 
}

使用方法：

<div id="divPhoto" onmousedown="drag(event,this)"></div>