首先贴上完整code（IE/FF）
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title></title>
<script type="text/javascript">
var Common = {
getEvent: function() {//ie/ff
if (document.all) {
return window.event;
}
func = getEvent.caller;
while (func != null) {
var arg0 = func.arguments[0];
if (arg0) {
if ((arg0.constructor == Event || arg0.constructor == MouseEvent) || (typeof (arg0) == "object" && arg0.preventDefault && arg0.stopPropagation)) {
return arg0;
}
}
func = func.caller;
}
return null;
},
getMousePos: function(ev) {
if (!ev) {
ev = this.getEvent();
}
if (ev.pageX || ev.pageY) {
return {
x: ev.pageX,
y: ev.pageY
};
}
if (document.documentElement && document.documentElement.scrollTop) {
return {
x: ev.clientX + document.documentElement.scrollLeft - document.documentElement.clientLeft,
y: ev.clientY + document.documentElement.scrollTop - document.documentElement.clientTop
};
}
else if (document.body) {
return {
x: ev.clientX + document.body.scrollLeft - document.body.clientLeft,
y: ev.clientY + document.body.scrollTop - document.body.clientTop
};
}
},
getItself: function(id) {
return "string" == typeof id ? document.getElementById(id) : id;
},
getViewportSize: { w: (window.innerWidth) ? window.innerWidth : (document.documentElement && document.documentElement.clientWidth) ? document.documentElement.clientWidth : document.body.offsetWidth, h: (window.innerHeight) ? window.innerHeight : (document.documentElement && document.documentElement.clientHeight) ? document.documentElement.clientHeight : document.body.offsetHeight },
isIE: document.all ? true : false,
setOuterHtml: function(obj, html) {
var Objrange = document.createRange();
obj.innerHTML = html;
Objrange.selectNodeContents(obj);
var frag = Objrange.extractContents();
obj.parentNode.insertBefore(frag, obj);
obj.parentNode.removeChild(obj);
}
}
///------------------------------------------------------------------------------------------------------
var Class = {
create: function() {
return function() { this.init.apply(this, arguments); }
}
}
var Drag = Class.create();
Drag.prototype = {
init: function(titleBar, dragDiv, Options) {
//设置点击是否透明，默认不透明
titleBar = Common.getItself(titleBar);
dragDiv = Common.getItself(dragDiv);
this.dragArea = { maxLeft: 0, maxRight: Common.getViewportSize.w - dragDiv.offsetWidth - 2, maxTop: 0, maxBottom: Common.getViewportSize.h - dragDiv.offsetHeight - 2 };
if (Options) {
this.opacity = Options.opacity ? (isNaN(parseInt(Options.opacity)) ? 100 : parseInt(Options.opacity)) : 100;
this.keepOrigin = Options.keepOrigin ? ((Options.keepOrigin == true || Options.keepOrigin == false) ? Options.keepOrigin : false) : false;
if (this.keepOrigin) { this.opacity = 50; }
if (Options.area) {
if (Options.area.left && !isNaN(parseInt(Options.area.left))) { this.dragArea.maxLeft = Options.area.left };
if (Options.area.right && !isNaN(parseInt(Options.area.right))) { this.dragArea.maxRight = Options.area.right };
if (Options.area.top && !isNaN(parseInt(Options.area.top))) { this.dragArea.maxTop = Options.area.top };
if (Options.area.bottom && !isNaN(parseInt(Options.area.bottom))) { this.dragArea.maxBottom = Options.area.bottom };
}
}
else {
this.opacity = 100, this.keepOrigin = false;
}
this.originDragDiv = null;
this.tmpX = 0;
this.tmpY = 0;
this.moveable = false;
var dragObj = this;
titleBar.onmousedown = function(e) {
var ev = e || window.event || Common.getEvent();
//只允许通过鼠标左键进行拖拽,IE鼠标左键为1 FireFox为0
if (Common.isIE && ev.button == 1 || !Common.isIE && ev.button == 0) {
}
else {
return false;
}
if (dragObj.keepOrigin) {
dragObj.originDragDiv = document.createElement("div");
dragObj.originDragDiv.style.cssText = dragDiv.style.cssText;
dragObj.originDragDiv.style.width = dragDiv.offsetWidth;
dragObj.originDragDiv.style.height = dragDiv.offsetHeight;
dragObj.originDragDiv.innerHTML = dragDiv.innerHTML;
dragDiv.parentNode.appendChild(dragObj.originDragDiv);
}
dragObj.moveable = true;
dragDiv.style.zIndex = dragObj.GetZindex() + 1;
var downPos = Common.getMousePos(ev);
dragObj.tmpX = downPos.x - dragDiv.offsetLeft;
dragObj.tmpY = downPos.y - dragDiv.offsetTop;
titleBar.style.cursor = "move";
if (Common.isIE) {
dragDiv.setCapture();
} else {
window.captureEvents(Event.mousemove);
}
dragObj.SetOpacity(dragDiv, dragObj.opacity);
//FireFox 去除容器内拖拽图片问题
if (ev.preventDefault) {
ev.preventDefault();
ev.stopPropagation();
}
document.onmousemove = function(e) {
if (dragObj.moveable) {
var ev = e || window.event || Common.getEvent();
//IE 去除容器内拖拽图片问题
if (document.all) //IE
{
ev.returnValue = false;
}
var movePos = Common.getMousePos(ev);
dragDiv.style.left = Math.max(Math.min(movePos.x - dragObj.tmpX, dragObj.dragArea.maxRight), dragObj.dragArea.maxLeft) + "px";
dragDiv.style.top = Math.max(Math.min(movePos.y - dragObj.tmpY, dragObj.dragArea.maxBottom), dragObj.dragArea.maxTop) + "px";
}
};
document.onmouseup = function() {
if (dragObj.keepOrigin) {
if (Common.isIE) {
dragObj.originDragDiv.outerHTML = "";
}
else {
Common.setOuterHtml(dragObj.originDragDiv, "");
}
}
if (dragObj.moveable) {
if (Common.isIE) {
dragDiv.releaseCapture();
}
else {
window.releaseEvents(dragDiv.mousemove);
}
dragObj.SetOpacity(dragDiv, 100);
titleBar.style.cursor = "default";
dragObj.moveable = false;
dragObj.tmpX = 0;
dragObj.tmpY = 0;
}
};
}
},
SetOpacity: function(dragDiv, n) {
if (Common.isIE) {
dragDiv.filters.alpha.opacity = n;
}
else {
dragDiv.style.opacity = n / 100;
}
},
GetZindex: function() {
var maxZindex = 0;
var divs = document.getElementsByTagName("div");
for (z = 0; z < divs.length; z++) {
maxZindex = Math.max(maxZindex, divs[z].style.zIndex);
}
return maxZindex;
}
}
window.onload = function() {
new Drag("dragDiv", "dragDiv", { opacity: 100, keepOrigin: true }); //, area: { left: 50, right: 500, top: 100, bottom: 400}
}
</script>
</head>
<body>
<div id="dragDiv" style="position:absolute; background-color:#FFFFFF;border:solid 1px #849BCA;width:200px;left:10px;top:10px;filter:alpha(opacity=100);opacity:1;">
<table cellpadding="0" cellspacing="0" border="0" style="width:100%;border-collapse:collapse; ">
<tr id="titleBar" style="height:22px; text-align:left; background-color:#547BC9;color:White; padding:3px;">
<th align="left" unselectable="on" >Title</th>
</tr>
<tr style="height:130px;padding:3px;" align="left" valign="top" unselectable="on">
<td><img src="http://images.cnblogs.com/logo_small.gif" alt="pic for drag" /> Content...</td> <!---->
</tr>
</table>
</div>
<div style="position:absolute; font-family:Tahoma;border:solid 1px #849BCA; background-color:#AAAAAA;width:200px;height:100px;left:210px;top:210px;filter:alpha(opacity=100);opacity:1; z-index:999">Are you able to cover me?</div>
</body>
</html>
对Drag的使用：在window.onload中，必填参数是titleBar和dragDiv，后者是要拖拽的容器，前者是拖拽容器的可拖拽部位，譬如经常遇到的通过标题栏拖动整个DIV，则titleBar即为改标题栏。而{ opacity: 100, keepOrigin: true , area: { left: 50, right: 500, top: 100, bottom: 400}} 是可选参数，用于扩展功能，opacity设置透明度，keepOrigin设置拖拽过程中是否保留原来拖拽容器，area设置拖拽范围。
- 拖拽的基本原理：当mousedown时记下鼠标点击位置离拖拽容器左边沿的距离和上边沿的距离，即tmpX,tmpY；mousemove时通过定位拖拽容器的style.left/style.top，使拖拽容器进行移动，定位到哪里则由刚刚的tmpX/tmpY和当前鼠标所在位置计算得出；mouseup时，结束移动。
- “var dragObj = this;” 这句是为了在mousedown/mouseup/mousemove事件里对Drag对象的相关变量进行引用。因为在mousedown里的this是titleBar,mouseup/mousemove里的this是document.
- 当拖拽速度太快导致鼠标移出拖拽容器，而拖拽容器位置未变，用document.mousemove代替titleBar.mousemove即可。
- 设置拖拽容器可拖拽的范围，若未设置，则默认为当前窗口可视范围。Note：在设置范围的时候使用Math.max/min来处理，而不是用If语句判断，用后者的话会导致快速拖拽时未达到容许范围边沿即停止的状况。
- 当拖拽过程中，可设置是否保留原来拖拽容器，当拖拽结束，隐藏原来容器，默认不保留。
- 当拖拽时，可设置拖拽的容器是否透明及透明度多少，默认不透明。但若拖拽过程中设置保留原来拖拽容器，即keepOrigin: true，则设置透明度为50%。
- 使右键、鼠标中键等不能拖动，仅左键单击可以拖动。Note：IE鼠标左键为event.Button=1 FireFox为event.Button=0.
- 解决如果点击在图片上无法拖拽的问题：非常杯具的是IE通过ev.returnValue = false来防止图片的事件，注意是放在document.onmousemove中，而FireFox通过ev.preventDefault();ev.stopPropagation(); 但是是放在titleBar的mousedown事件中。
- 有一种情况，当浏览器窗口不是最大化的时候，你希望当鼠标在浏览器外移动时，浏览器里的拖拽容器仍然移动，这时就要使用鼠标事件捕获，IE中相应的是dragDiv.setCapture();与dragDiv.releaseCapture(); FF中是window.captureEvents(Event.mousemove);与window.releaseEvents(dragDiv.mousemove) 。
- 确保每次拖拽时拖拽容器的zindex都不会被其他块元素覆盖。
转载于:https://www.cnblogs.com/T00PCN/archive/2010/04/27/1722125.html