JS基础——数据类型判断typeof、instanceof、Object.prototype.toString

1. typeof用在基本数据类型和函数时，返回其对应类型的描述，对于引用类型都返回为object.
2. instanceof没法判断基本数据类型，对于引用类型数据，返回其其对应类型。
3. Object.prototype.toString不管基本数据类型仍是引用类型返回其对应类型。

对应测试结果以下：

	typeof test	instanceof	Object.prototype.toString.call(test)
var test = 'xuriliang';	string	test instanceof String //false	[object String]
var test = 27;	number	test instanceof Number //false	[object Number]
var test = true;	boolean	test instanceof Boolean //false	[object Boolean]
var test = [1,2,3];	object	test instanceof Array //true	[object Array]
		test instanceof Object //true
var test = null;	object	test instanceof Object //false	[object Null]
var test = undefined;	undefined	test instanceof Object //false	[object Undefined]
var test = new String('xuriliang')	object	test instanceof String //true	[object String]
		test instanceof Object //true
var test = new Number(27)	object	test instanceof Number //true	[object Number]
		test instanceof Object //true
var test = new Boolean(true)	object	test instanceof Boolean //true	[object Boolean]
		test instanceof Object //true
var test = new Array(1,2,3)	object	test instanceof Array //true	[object Array]
		test instanceof Object //true
var test = function(){}	function	test instanceof Function //true	[object Function]
		test instanceof Object //true
var test = /d/	object	test instanceof RegExp //true	[object RegExp]
		test instanceof Object //true