这一段是什么意思

function typeOf(ele) {
            var r;
            if (ele === null) {r = "null"}
            else if (ele instanceof Array) {r = "array"}
            else if (ele === window) {r = "window"}
            else if (ele instanceof Date) {r = "date"}
            else {r = typeof ele};
            return r;
        }

如果typeof是object,这样判断怎么知道具体像是date，window有多少呢？