javascript obj type (typeof extend)

var a={};
    a.a=1;
    a.b="ccc";
    a.c=new Date();
    a.d={};
    a.e=1.23;
    a.f=[];
    a.h=null;
    a.i=undefined;
    var i;
    for(i in a){
        console.log("typeof "+i+" is: "+typeof(a[i])+"            "+Object.prototype.toString.call(a[i]));
    }

输出

typeof a is: number            [object Number]
typeof b is: string               [object String]
typeof c is: object               [object Date]
typeof d is: object               [object Object]
typeof e is: number            [object Number]
typeof f is: object                [object Array]
typeof g is: function            [object Function]
typeof h is: object               [object Null]
typeof i is: undefined          [object Undefined]