js 判断数据类型的几种方法

var a = "iamstring.";
var b = 222;
var c= [1,2,3];
var d = new Date();
var e = function(){alert(111);};
var f = function(){this.name="22";};　　

alert(typeof a)  ------------> string
alert(typeof b)  ------------> number
alert(typeof c)  ------------> object
alert(typeof d)  ------------> object
alert(typeof e)  ------------> function
alert(typeof f)  ------------> function

alert(typeof a == "string") -------------> true
alert(typeof a == String) ---------------> false

alert(c instanceof Array) ---------------> true
alert(d instanceof Date)
alert(f instanceof Function) ------------> true
alert(f instanceof function) ------------> false

   function A(){};
   function B(){};
   A.prototype = new B(); //A继承自B
   var aObj = new A();
   alert(aobj.constructor === B) -----------> true;
   alert(aobj.constructor === A) -----------> false;

   alert(aobj instanceof B) ----------------> true;
   alert(aobj instanceof B) ----------------> true;

   aobj.constructor = A; //将自己的类赋值给对象的constructor属性
   alert(aobj.constructor === A) -----------> true;
   alert(aobj.constructor === B) -----------> false; //基类不会报true了;

alert(Object.prototype.toString.call(a) === ‘[object String]') -------> true;
alert(Object.prototype.toString.call(b) === ‘[object Number]') -------> true;
alert(Object.prototype.toString.call(c) === ‘[object Array]') -------> true;
alert(Object.prototype.toString.call(d) === ‘[object Date]') -------> true;
alert(Object.prototype.toString.call(e) === ‘[object Function]') -------> true;
alert(Object.prototype.toString.call(f) === ‘[object Function]') -------> true;

jQuery.type( undefined ) === "undefined"
jQuery.type() === "undefined"
jQuery.type( window.notDefined ) === "undefined"
jQuery.type( null ) === "null"

jQuery.type( true ) === "boolean"
jQuery.type( 3 ) === "number"
jQuery.type( "test" ) === "string"
jQuery.type( function(){} ) === "function"
jQuery.type( [] ) === "array"
jQuery.type( new Date() ) === "date"
jQuery.type( new Error() ) === "error" // as of jQuery 1.9
jQuery.type( /test/ ) === "regexp"