经典的js dom拖拽类

/**************************************************
* dom-drag.js
* 09.25.2001
* www.youngpup.net
**************************************************
* 10.28.2001 - fixed minor bug where events
* sometimes fired off the handle, not the root.
**************************************************/

var Drag = {

    obj : null,

    init : function(o, oRoot, minX, maxX, minY, maxY, bSwapHorzRef, bSwapVertRef, fXMapper, fYMapper)
    {
        o.onmousedown    = Drag.start;

        o.hmode            = bSwapHorzRef ? false : true ;
        o.vmode            = bSwapVertRef ? false : true ;

        o.root = oRoot && oRoot != null ? oRoot : o ;

        if (o.hmode  && isNaN(parseInt(o.root.style.left  ))) o.root.style.left   = "0px";
        if (o.vmode  && isNaN(parseInt(o.root.style.top   ))) o.root.style.top    = "0px";
        if (!o.hmode && isNaN(parseInt(o.root.style.right ))) o.root.style.right  = "0px";
        if (!o.vmode && isNaN(parseInt(o.root.style.bottom))) o.root.style.bottom = "0px";

        o.minX    = typeof minX != 'undefined' ? minX : null;
        o.minY    = typeof minY != 'undefined' ? minY : null;
        o.maxX    = typeof maxX != 'undefined' ? maxX : null;
        o.maxY    = typeof maxY != 'undefined' ? maxY : null;

        o.xMapper = fXMapper ? fXMapper : null;
        o.yMapper = fYMapper ? fYMapper : null;

        o.root.onDragStart    = new Function();
        o.root.onDragEnd    = new Function();
        o.root.onDrag        = new Function();
    },

    start : function(e)
    {
        var o = Drag.obj = this;
        e = Drag.fixE(e);
        var y = parseInt(o.vmode ? o.root.style.top  : o.root.style.bottom);
        var x = parseInt(o.hmode ? o.root.style.left : o.root.style.right );
        o.root.onDragStart(x, y);

        o.lastMouseX    = e.clientX;
        o.lastMouseY    = e.clientY;

        if (o.hmode) {
            if (o.minX != null)    o.minMouseX    = e.clientX - x + o.minX;
            if (o.maxX != null)    o.maxMouseX    = o.minMouseX + o.maxX - o.minX;
        } else {
            if (o.minX != null) o.maxMouseX = -o.minX + e.clientX + x;
            if (o.maxX != null) o.minMouseX = -o.maxX + e.clientX + x;
        }

        if (o.vmode) {
            if (o.minY != null)    o.minMouseY    = e.clientY - y + o.minY;
            if (o.maxY != null)    o.maxMouseY    = o.minMouseY + o.maxY - o.minY;
        } else {
            if (o.minY != null) o.maxMouseY = -o.minY + e.clientY + y;
            if (o.maxY != null) o.minMouseY = -o.maxY + e.clientY + y;
        }

        document.onmousemove    = Drag.drag;
        document.onmouseup        = Drag.end;

        return false;
    },

    drag : function(e)
    {
        e = Drag.fixE(e);
        var o = Drag.obj;

        var ey    = e.clientY;
        var ex    = e.clientX;
        var y = parseInt(o.vmode ? o.root.style.top  : o.root.style.bottom);
        var x = parseInt(o.hmode ? o.root.style.left : o.root.style.right );
        var nx, ny;

        if (o.minX != null) ex = o.hmode ? Math.max(ex, o.minMouseX) : Math.min(ex, o.maxMouseX);
        if (o.maxX != null) ex = o.hmode ? Math.min(ex, o.maxMouseX) : Math.max(ex, o.minMouseX);
        if (o.minY != null) ey = o.vmode ? Math.max(ey, o.minMouseY) : Math.min(ey, o.maxMouseY);
        if (o.maxY != null) ey = o.vmode ? Math.min(ey, o.maxMouseY) : Math.max(ey, o.minMouseY);

        nx = x + ((ex - o.lastMouseX) * (o.hmode ? 1 : -1));
        ny = y + ((ey - o.lastMouseY) * (o.vmode ? 1 : -1));

        if (o.xMapper)        nx = o.xMapper(y)
        else if (o.yMapper)    ny = o.yMapper(x)

        Drag.obj.root.style[o.hmode ? "left" : "right"] = nx + "px";
        Drag.obj.root.style[o.vmode ? "top" : "bottom"] = ny + "px";
        Drag.obj.lastMouseX    = ex;
        Drag.obj.lastMouseY    = ey;

        Drag.obj.root.onDrag(nx, ny);
        return false;
    },

    end : function()
    {
        document.onmousemove = null;
        document.onmouseup   = null;
        Drag.obj.root.onDragEnd(    parseInt(Drag.obj.root.style[Drag.obj.hmode ? "left" : "right"]),
                                    parseInt(Drag.obj.root.style[Drag.obj.vmode ? "top" : "bottom"]));
        Drag.obj = null;
    },

    fixE : function(e)
    {
        if (typeof e == 'undefined') e = window.event;
        if (typeof e.layerX == 'undefined') e.layerX = e.offsetX;
        if (typeof e.layerY == 'undefined') e.layerY = e.offsetY;
        return e;
    }
};

使用方法：

Drag.init(div1, div2);

第一个参数是拖拽的div，第二个参数是随着拖拽飘动的div。