function drag(obj) {                obj.onmousedown = function(ev) {            var ev = ev || event;                        var disX = ev.clientX - this.offsetLeft;            var disY = ev.clientY - this.offsetTop;                        if ( obj.setCapture ) {                obj.setCapture();            }                        document.onmousemove = function(ev) {                var ev = ev || event;                                obj.style.left = ev.clientX - disX + ‘px‘;                obj.style.top = ev.clientY - disY + ‘px‘;            }                        document.onmouseup = function() {                document.onmousemove = document.onmouseup = null;                //释放全局捕获 releaseCapture();                if ( obj.releaseCapture ) {                    obj.releaseCapture();                }            }                        return false;                    }            }