拖拽效果

var odiv = document.getElementById("box");
var disX = 0;
var disY = 0;
odiv.onmousedown = function(ev){
var ev = ev || window.event;
disX = ev.clientX -odiv.offsetLeft;
disY = ev.clientY -odiv.offsetTop;
document.onmousemove = function(ev){
var ev = ev || window.event;
odiv.style.left = ev.clientX - disX + 'px';
odiv.style.top = ev.clientY - disY + 'px';
}
document.onmouseup = function(){
document.onmousemove = null;
document.onmouseup = null;
}
}