简单的jquery拖曵原理js特效实例

<!DOCTYPE html>
<html>
<title>简单拖曵原理实例</title>
<script language="javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
    <script type="text/javascript">
        $(function(){
            //样式
            $("#drag").css({"position":"absolute","top":"100px","left":"100px","border":"1px solid #789","width":"150px","height":"90px","background":"#988f82","cursor":"move"})

            /*+++++ 拖曳效果 ++++++
            *原理：标记拖曳状态dragging ,坐标位置iX, iY
            *         mousedown:fn(){dragging = true, 记录起始坐标位置，设置鼠标捕获}
            *         mouseover:fn(){判断如果dragging = true, 则当前坐标位置 - 记录起始坐标位置，绝对定位的元素获得差值}
            *         mouseup:fn(){dragging = false, 释放鼠标捕获，防止冒泡}
            */
            var dragging = false;
            var iX, iY;

            $("#drag").mousedown(function(e) {
                dragging = true;
                iX = e.clientX - this.offsetLeft;
                iY = e.clientY - this.offsetTop;
                this.setCapture && this.setCapture();
                return false;
            });

            document.onmousemove = function(e) {
                if (dragging) {
                var e = e || window.event;
                var oX = e.clientX - iX;
                var oY = e.clientY - iY;
                $("#drag").css({"left":oX + "px", "top":oY + "px"});
                return false;
                }
            };

            $(document).mouseup(function(e) {
                dragging = false;
                $("#drag")[0].releaseCapture();
                e.cancelBubble = true;
            })

        })

    </script>
</head>

<body>
    <div id="drag"></div>
</body>
</html>