jquery 实现简单拖拽

$.fn.drag = function(obj) {

    var dragging = false;
    var oDrag = $(obj);

    oDrag.mousedown(function(e) {

        dragging = true;

        var disX = e.pageX - oDrag.offset().left;
        var disY = e.pageY - oDrag.offset().top;

        oDrag.css('position','absolute');

        $(document).mousemove(function(e) {

            if(dragging) {

                var leftPos = e.pageX - disX;
                var rightPos = e.pageY - disY;

                oDrag.css({'left': leftPos + 'px', 'top': rightPos + 'px'});
                return false;

            }

        }).mouseup(function(e) {

            dragging = false;
            //oDrag.css({'position':'','left':'','top':''});
            e.cancelBubble = true;

        });

    });
}
$.fn.drag(obj);