var Type={};
//type=["String","Array","Number"][i++]这不成了一个复合数组了吗？？不太理解
for(var i=0,type;type=["String","Array","Number"][i++];){
    (function(type){
     Type["is"+type]=function(obj){
        return Object.prototype.toString.call(obj)==='[object]'+type+']';
     }
    })(type);
}
alert(Type.isArray([]));
alert(Type.isString("str"));