[读码时间] 完美拖拽

说明：代码取自网络，注释为原文所有！
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>完美拖拽</title>
    <style type="text/css">
        html, body {
            overflow: hidden;
        }

        body, div, h2, p {
            margin: 0;
            padding: 0;
        }

        body {
            color: #fff;
            background: #000;
            font: 12px/2 Arial;
        }

        p {
            padding: 0 10px;
            margin-top: 10px;
        }

        span {d
            color: #ff0;
            padding-left: 5px;
        }

        #box {
            position: absolute;
            width: 300px;
            height: 150px;
            background: #333;
            border: 2px solid #ccc;
            top: 50%;
            left: 50%;
            margin: -75px 0 0 -150px;
        }

            #box h2 {
                height: 25px;
                cursor: move;
                background: #222;
                border-bottom: 2px solid #ccc;
                text-align: right;
                padding: 0 10px;
            }

                #box h2 a {
                    color: #fff;
                    font: 12px/25px Arial;
                    text-decoration: none;
                    outline: none;
                }
    </style>
    <script type="text/javascript">
window.onload=function ()
{
    var oBox=document.getElementById("box");
    var oH2 = oBox.getElementsByTagName("h2")[0];
    var oA = oBox.getElementsByTagName("a")[0];
    var aSpan = oBox.getElementsByTagName("span");
    var disX = disY = 0;
    var bDrag = false;
    var aPos = [{x:oBox.offsetLeft, y:oBox.offsetTop}]

    //鼠标按下, 激活拖拽
    oH2.onmousedown = function (event)
    {
        var event = event || window.event;
        bDrag = true;
        disX = event.clientX - oBox.offsetLeft;
        disY = event.clientY - oBox.offsetTop;

        aPos.push({x:oBox.offsetLeft, y:oBox.offsetTop})

        this.setCapture && this.setCapture();

        return false
    };

    //拖拽开始
    document.onmousemove = function (event)
    {
        if (!bDrag) return;
        var event = event || window.event;
        var iL = event.clientX - disX;
        var iT = event.clientY - disY;
        var maxL = document.documentElement.clientWidth - oBox.offsetWidth;
        var maxT = document.documentElement.clientHeight - oBox.offsetHeight;

        iL = iL < 0 ? 0 : iL;
        iL = iL > maxL ? maxL : iL;

        iT = iT < 0 ? 0 : iT;
        iT = iT > maxT ? maxT : iT;

        oBox.style.marginTop = oBox.style.marginLeft = 0;
        oBox.style.left = iL + "px";
        oBox.style.top = iT + "px";

        aPos.push({x:iL, y:iT})

        status();

        return false
    };

    //鼠标释放, 结束拖拽
    document.onmouseup = window.onblur = oH2.onlosecapture = function ()
    {
        bDrag = false;
        oH2.releaseCapture && oH2.releaseCapture();
        status()
    };

    //回放拖动轨迹
    oA.onclick = function ()
    {
        if (aPos.length == 1) return;
        var timer = setInterval(function ()
        {
            var oPos = aPos.pop();
            oPos ? (oBox.style.left = oPos.x + "px", oBox.style.top = oPos.y + "px", status()) : clearInterval(timer)
        }, 30);

        this.focus = false;//去除链接虚线

        return false
    };

    //阻止冒泡
    oA.onmousedown = function (event)
    {
        (event || window.event).cancelBubble = true
    };

    //监听状态函数
    function status ()
    {
        aSpan[0].innerHTML = bDrag;
        aSpan[1].innerHTML = oBox.offsetTop;
        aSpan[2].innerHTML = oBox.offsetLeft
    }

    //初始调用
    status()
};
    </script>
</head>
<body>
    <div id="box">
        <h2><a href="javascript:;">点击回放拖动轨迹</a></h2>
        <p><strong>Drag:</strong><span></span></p>
        <p><strong>offsetTop:</strong><span></span></p>
        <p><strong>offsetLeft:</strong><span></span></p>
    </div>
</body>
</html>
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