JS 拖动DIV 需要JQUERY 支持

<!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>自由拖动的DIV层方块</title>
    <meta http-equiv="content-type" content="text/html;charset=gb2312">
    <script type="text/javascript" src="js/jquery.min.js"></script>
    <style type="text/css">
        #draggable {
            background-color: green;
            font-size: 9pt;
            padding: 30px;
            color: white;
            width: 360px;
            height: 224px;
            position: absolute;
        }
    </style>
    <script type="text/javascript">
        var Drager = function () {
            
        };
        Drager.dom = null;
        Drager.selector = null;
        Drager.prototype.xdrag = function (dom, selector) {
            var obj = this;
            obj.selector = selector;
            dom.onmousedown = function (e) {
                e = obj.getEvent(e);
                e.preventDefault && e.preventDefault();
                obj.dom  = this;
                obj.dom.x = e.clientX+$(window).scrollLeft() - obj.dom.offsetLeft;
                obj.dom.y = e.clientY + $(window).scrollTop() - obj.dom.offsetTop;
                document.onmousemove = function (e) { obj.move(e, obj); };
                document.onmouseup = function (e) { obj.end(e, obj); };
            };
        };
        Drager.prototype.getEvent = function (e) {
            if (!e) {
                e = window.event;
                e.target = e.srcElement;
                e.layerX = e.offsetX;
                e.layerY = e.offsetY;
            }
            return e;
        };
        Drager.prototype.move = function (e,srcObj) {
            
            e = srcObj.getEvent(e);
            var oLeft, oTop;
            oLeft = e.clientX + $(window).scrollLeft() - srcObj.dom.x;
            oTop = e.clientY + $(window).scrollTop() - srcObj.dom.y;

            
            if (srcObj.selector != null) {
                if (oLeft > parseInt( srcObj.dom.style.left)) {
                    if (oLeft + $(srcObj.dom).outerWidth() > $(srcObj.selector).offset().left + $(srcObj.selector).outerWidth()) {
                        oLeft = $(srcObj.selector).offset().left + $(srcObj.selector).outerWidth() - $(srcObj.dom).outerWidth();
                    }
                } else if (oLeft < parseInt(srcObj.dom.style.left)) {
                    if (oLeft < $(srcObj.selector).offset().left ) {
                        oLeft = $(srcObj.selector).offset().left ;
                    }
                }
                if (oTop > parseInt(srcObj.dom.style.top)) {
                    if (oTop + $(srcObj.dom).outerHeight() > $(srcObj.selector).offset().top + $(srcObj.selector).outerHeight()) {
                        oTop = $(srcObj.selector).offset().top + $(srcObj.selector).outerHeight() - $(srcObj.dom).outerHeight();
                    }
                } else if (oTop < parseInt(srcObj.dom.style.top)) {
                    if (oTop < $(srcObj.selector).offset().top) {
                        oTop = $(srcObj.selector).offset().top;
                    }
                }
            }
            srcObj.dom.style.left = oLeft + 'px';
            srcObj.dom.style.top = oTop + 'px';
        };
        Drager.prototype.end = function (e,srcObj) {
            e = srcObj.getEvent(e);
            srcObj.dom = document.onmousemove = document.onmouseup = null;
        };
       
        var drag = new Drager();
    </script>
    <script type="text/javascript">
       
        window.onload = function () {
            var obj = document.getElementById('draggable');
            //第二个参数是限制范围，可不填
            drag.xdrag(obj,".container");
        }
        
    </script>
</head>
<body>
    <div class="container" style="800px;height:500px; background-color:red;">
        <div id="draggable">这个可以拖动！</a></div>
    </div>
    
</body>
</html>
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原文地址：https://www.cnblogs.com/xdoudou/p/3664487.html