JS拖动技术--- 关于setCapture

<script type="text/javascript">

<!--

window.onload=function(){

objDiv = document.getElementById('drag');

drag(objDiv);

};

function drag(dv){

dv.onmousedown=function(e){

var d=document;

e = e || window.event;

var x= e.layerX || e.offsetX;

var y= e.layerY || e.offsetY;

//设置捕获范围

if(dv.setCapture){

dv.setCapture();

}else if(window.captureEvents){

window.captureEvents(Event.MOUSEMOVE | Event.MOUSEUP);

}

d.onmousemove=function(e){

e= e || window.event;

if(!e.pageX)e.pageX=e.clientX;

if(!e.pageY)e.pageY=e.clientY;

var tx=e.pageX-x;

var ty=e.pageY-y;

dv.style.left=tx;

dv.style.top=ty;

};

d.onmouseup=function(){

//取消捕获范围

if(dv.releaseCapture){

dv.releaseCapture();

}else if(window.captureEvents){

window.captureEvents(Event.MOUSEMOVE|Event.MOUSEUP);

}

//清除事件

d.onmousemove=null;

d.onmouseup=null;

};

};

}

//-->

</script>

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<div id="drag" >drag me <div>