这段js代码会让页面所有position:absolute;的元素可以拖动

var chef = (function(){        var drawDiv,ofstX,ofstY;        function fun(event){            var event = event || window.event;            var target = event.target || event.srcElement;            switch(event.type){                case "mousedown":                            drawDiv = target;                            ofstX = event.clientX-drawDiv.offsetLeft;                            ofstY = event.clientY-drawDiv.offsetTop;                    break;                case "mousemove":                        if(drawDiv != null){                            drawDiv.style.left = event.clientX - ofstX + "px";                            drawDiv.style.top = event.clientY - ofstY + "px";                        }                    break;                case "mouseup":                    drawDiv = null;                    break;            }        };        document.body.onmousedown = function(event){fun(event);};        document.body.onmousemove = function(event){fun(event);};        document.body.onmouseup   = function(event){fun(event);};    })();