获得dom元素的宽和高

 var param = i ? "Height" : "Width";
            if (elem === win) {
                var de = doc.documentElement;
                rt = self["inner" + param] || (de && de["client" + param]) || doc.body["client" + param];
            }
            else if (elem === doc) {
                rt = doc.body["scroll" + param];
            }
            //为none时获取不到宽度
            else if (getRealStyle(elem, "display") !== "none") {
                rt = elem["offset" + param] || elem["client" + param];
            }
            else {
                var style = elem.style,
                    temp =  style.display;
                style.display = "block"; 很重要
                rt = elem["offset" + param] || elem["client" + param];
                style.display = temp;
            }
            return rt;

        }