可拖动DIV层

var oBox=document.getElementById("divID"); //拖动层
var disX = disY = 0;
var bDrag = false;
//激活拖动
oBox.onmousedown = function (event){
var event = event || window.event;
bDrag = true;
disX = event.clientX - oBox.offsetLeft;
disY = event.clientY - oBox.offsetTop;
this.setCapture && this.setCapture();
return false;
};
//拖动开始
document.onmousemove = function (event){
if (!bDrag) return;
var event = event || window.event;
var iL = event.clientX - disX;
var iT = event.clientY - disY;
var minL = 0;
var minT = 0;
var maxL = window.screen.width;
var maxT = window.screen.height;
iL = iL < minL ? minL : iL;
iL = iL > maxL ? maxL : iL;
iT = iT < minT ? minT : iT;
iT = iT > maxT ? maxT : iT;
oBox.style.marginTop = oBox.style.marginLeft = 0;
oBox.style.left = iL + "px";
oBox.style.top = iT + "px";
return false;
};
//结束拖动
document.onmouseup =oBox.onlosecapture = function (){
bDrag = false;
oBox.releaseCapture && oBox.releaseCapture();
};