可拖动div

客户要求，页面有图片并且可以随意拖动

具体实现：

css：

#div1{
width: 30px;
height: 30px;
/*一定要绝对定位*/
position: absolute;
/*初始位置*/
left: 5%;
}

js：

window.onload = function(){
var div1 = document.getElementById("div1");
div1.onmousedown = function(ev){
var oevent = ev || event;
var distanceX = oevent.clientX - div1.offsetLeft;
var distanceY = oevent.clientY - div1.offsetTop;
document.onmousemove = function(ev){
var oevent = ev || event;
div1.style.left = oevent.clientX - distanceX + 'px';
div1.style.top = oevent.clientY - distanceY + 'px';
};
document.onmouseup = function(){
document.onmousemove = null;
document.onmouseup = null;
};
};
};

jsp：

<div id="div1" class="first" style="left: 3%;bottom: 37%">
<img src="<%=path %>/frame/images/fxsj.png" style="width: 80px;height: 80px" class="fxsj" />
</div>