一个js拖拽的效果类和dom-drag.js浅析_javascript技巧

/**************************************************
* Drag.js
* 作者：橡树小屋 07.17.2010
* http://www.cnblogs.com/babyzone2004/
*用法：Drag.initDrag(id); id是标签的id名称
**************************************************/
var Drag={
dragObject:null,
mouseOffset:null,
initDrag:function(item){
if(item){
this.item=document.getElementById(item);
this.item.onmousedown=function(evnt){
document.onmousemove=Drag.mouseMove;
document.onmouseup=Drag.mouseUp;
Drag.dragObject=this;
Drag.mouseOffset=Drag.getMouseOffset(this,evnt);
return false;
}
}
},
mousePoint:function(x,y){
this.x=x;
this.y=y;
},
mousePosition:function (evnt){
evnt=evnt||window.event;
var x=parseInt(evnt.clientX);
var y=parseInt(evnt.clientY);
return new Drag.mousePoint(x,y);
},
getMouseOffset:function(target,evnt){
var mousePos=Drag.mousePosition(evnt);
var x=mousePos.x-target.offsetLeft;
var y=mousePos.y-target.offsetTop;
return new Drag.mousePoint(x,y);
},
mouseUp:function (evnt){
Drag.dragObject=null;
document.onmousemove = null;
document.onmouseup = null;
},
mouseMove:function(evnt){
if(!Drag.dragObject) return;
var mousePos=Drag.mousePosition(evnt);
Drag.dragObject.style.position="absolute";
Drag.dragObject.style.top=mousePos.y-Drag.mouseOffset.y+"px";
Drag.dragObject.style.left=mousePos.x-Drag.mouseOffset.x+"px";
return false;
}
}