/****************************************
A more useful version of `typeof` and functions to test if a parameter is of a specified type.

Inspired by http://snipplr.com/view/1996/typeof--a-more-specific-typeof/

Examples:

var u;
is.Undefined(u)	//true
is.Number(u)	//false

var n=1;
is.Number(n)	//true; note that (n instanceof Number) would be false since n is a literal
is.Object(n)	//true
/****************************************/

var is = new (function(){
	var undefined;
	function test(type)
	{
		return function(o){
				return (o instanceof type || 
					(o !== undefined && !(o instanceof Object) /*i.e., it's a literal*/ && o.constructor === type));
			};
	}
	
	this.Undefined = function(o){ return o === undefined; };
	this.Null = function(o){ return o === null; };
	this.Boolean = test(Boolean);
	this.Number = test(Number);
	this.String = test(String);
	this.RegExp = function(o){ return (o instanceof RegExp); };
	this.Date = function(o){ return (o instanceof Date); };
	this.Array = function(o){ return (o instanceof Array); };
	this.Function = function(o){ return (o instanceof Function); };
	this.Object = function(o){ return (o instanceof Object || this.Boolean(o) || this.Number(o) || this.String(o)); };
})();

//note that if argument `o` is an instance of more than one data type (which can happen if you mess with prototypes),
// only the first type tested will be returned
function typeOf(o)
{
	for(var type in is){ if(type != "Object" && is[type](o)) return type.toLowerCase(); }
	if(is.Object(o)) return "object";
	return "";
}

/*
//test all data types
//it's worth noting that, in IE, an HTML element is not considered an instance of Object
var u;
function f(){ this.toString=function(){return "[object f]"} };
var h = document.createElement("div");
var a = [u, null, true, (new Boolean), 1, (new Number), "s", (new String), /r/, (new RegExp), (new Date), [0,1], (new Array), 
	f, function(){}, (new Function), {}, (new Object), (new f), h];
for(var i=0; i<a.length; i++)
{
	console.log(a[i]+" : "+typeOf(a[i]));
}
*/

/****************************************
A more useful version of `typeof` and functions to test if a parameter is of a specified type.

Inspired by http://snipplr.com/view/1996/typeof--a-more-specific-typeof/

Examples:

var u;
is.Undefined(u)	//true
is.Number(u)	//false

var n=1;
is.Number(n)	//true; note that (n instanceof Number) would be false since n is a literal
is.Object(n)	//true
/****************************************/

var is = new (function(){
	var undefined;
	function test(type)
	{
		return function(o){
				return (o instanceof type || 
					(o !== undefined && !(o instanceof Object) /*i.e., it's a literal*/ && o.constructor === type));
			};
	}
	
	this.Undefined = function(o){ return o === undefined; };
	this.Null = function(o){ return o === null; };
	this.Boolean = test(Boolean);
	this.Number = test(Number);
	this.String = test(String);
	this.RegExp = test(RegExp);
	this.Date = test(Date);
	this.Array = test(Array);
	this.Function = test(Function);
	this.Object = test(Object);
})();

//note that if argument `o` is an instance of more than one data type (which can happen if you mess with prototypes),
// only the first type tested will be returned
function typeOf(o)
{
	for(var type in is){ if(is[type](o)) return type.toLowerCase(); }
}

/*
//test all data types
var u;
function f(){ this.toString=function(){return "[object f]"} };
var g = new f;
var a = [u, null, true, (new Boolean), 1, (new Number), "s", (new String), /r/, (new RegExp), (new Date), [0,1], (new Array), 
	f, function(){}, (new Function), {}, (new Object), g];
for(var i=0; i<a.length; i++)
{
	console.log(a[i]+" : "+typeOf(a[i]));
}
*/

/****************************************/
A more useful version of `typeof` and functions to test if a parameter is of a specified type.

Inspired by http://snipplr.com/view/1996/typeof--a-more-specific-typeof/

Examples:

var u;
is.Undefined(u)	//true
is.Number(u)	//false

var n=1;
is.Number(n)	//true; note that (n instanceof Number) would be false since n is a literal
is.Object(n)	//true
/****************************************/

var is = new (function(){
	var undefined;
	function test(type)
	{
		return function(o){
				return (o instanceof type || 
					(o !== undefined && !(o instanceof Object) /*i.e., it's a literal*/ && o.constructor === type));
			};
	}
	
	this.Undefined = function(o){ return o === undefined; };
	this.Null = function(o){ return o === null; };
	this.Boolean = test(Boolean);
	this.Number = test(Number);
	this.String = test(String);
	this.RegExp = test(RegExp);
	this.Date = test(Date);
	this.Array = test(Array);
	this.Function = test(Function);
	this.Object = test(Object);
})();

//note that if argument `o` is an instance of more than one data type (which can happen if you mess with prototypes),
// only the first type tested will be returned
function typeOf(o)
{
	for(var type in is){ if(is[type](o)) return type.toLowerCase(); }
}

/*
//test all data types
var u;
function f(){ this.toString=function(){return "[object f]"} };
var g = new f;
var a = [u, null, true, (new Boolean), 1, (new Number), "s", (new String), /r/, (new RegExp), (new Date), [0,1], (new Array), 
	f, function(){}, (new Function), {}, (new Object), g];
for(var i=0; i<a.length; i++)
{
	console.log(a[i]+" : "+typeOf(a[i]));
}
*/

//inspired by http://snipplr.com/view/1996/typeof--a-more-specific-typeof/

var is = new (function(){
	var undefined;
	function test(type)
	{
		return function(o){
				return (o instanceof type || 
					(o !== undefined && !(o instanceof Object) /*i.e., it's a literal*/ && o.constructor === type));
			};
	}
	
	this.Undefined = function(o){ return o === undefined; };
	this.Null = function(o){ return o === null; };
	this.Boolean = test(Boolean);
	this.Number = test(Number);
	this.String = test(String);
	this.RegExp = test(RegExp);
	this.Date = test(Date);
	this.Array = test(Array);
	this.Function = test(Function);
	this.Object = test(Object);
})();

//note that if argument `o` is an instance of more than one data type (which can happen if you mess with prototypes),
// only the first type tested will be returned
function typeOf(o)
{
	for(var type in is){ if(is[type](o)) return type.toLowerCase(); }
}

/*
//test all data types
var u;
function f(){ this.toString=function(){return "[object f]"} };
var g = new f;
var a = [u, null, true, (new Boolean), 1, (new Number), "s", (new String), /r/, (new RegExp), (new Date), [0,1], (new Array), 
	f, function(){}, (new Function), {}, (new Object), g];
for(var i=0; i<a.length; i++)
{
	console.log(a[i]+" : "+typeOf(a[i]));
}
*/

A more useful version of `typeof` and functions to test if a parameter is of a specified type.

JavaScript Type Tests

javascript

JavaScript