1 console.log(typeof 2); // number
2 console.log(typeof "2"); // string
3 console.log(typeof true); // boolean
4 console.log(typeof [2]); // object
5 console.log(typeof {name:2});// object
6 console.log(typeof function(){return 2});// function
7 console.log(typeof new Date());// object
8 console.log(typeof null); // object
9 console.log(typeof undefined);// undefined

 1 var getType = Object.prototype.toString;
 2 var res = getType.call(2);
 3 res = getType.call("2");
 4 res = getType.call(true);
 5 res = getType.call([2]);
 6 res = getType.call({name:2});
 7 res = getType.call(function(){});
 8 res = getType.call(new Date());
 9 res = getType.call(null);
10 res = getType.call(undefined);

1 [object Number]
2 [object String]
3 [object Boolean]
4 [object Array]
5 [object Object]
6 [object Function]
7 [object Date]
8 [object Null]
9 [object Undefined]