I think it might be only performance case - http://jsperf.com/comparing-underscore-js-isfunction-with-typeof-function/2

And seems that ``typeof`` is faster.. so my question is - which is more appropriate to use?

_.isFunction(a) vs. typeof a === &#39;function&#39;? javascript

Is there a better way to get the type of a variable in JS than `typeof`? It works fine when you do:

    &gt; typeof 1
    &quot;number&quot;
    &gt; typeof &quot;hello&quot;
    &quot;string&quot;

But it&#39;s useless when you try:
    
    &gt; typeof [1,2]
    &quot;object&quot;
    &gt;r = new RegExp(/./)
    /./
    &gt; typeof r
    &quot;function&quot;

I know of `instanceof`, but this requires you to know the type beforehand.    

    &gt; [1,2] instanceof Array
    true
    &gt; r instanceof RegExp
    true

Is there a better way?

Better way to get type of a Javascript variable?

Is there a &quot;typeof&quot; like function in Java that returns the type of a primitive data type (PDT) variable or an expression of operands PDTs?

`instanceof` seems to work for class types only.




How to determine the primitive type of a primitive variable?

&gt; **Possible Duplicate:**  
&gt; [C# - Is there a better alternative than this to &amp;#39;switch on type&amp;#39;?](https://stackoverflow.com/questions/298976/c-sharp-is-there-a-better-alternative-than-this-to-switch-on-type)  

&lt;!-- End of automatically inserted text --&gt;

C# doesn&#39;t support switching on the type of an object.  
What is the best pattern of simulating this:

    switch (typeof(MyObj))
        case Type1:
        case Type2:
        case Type3:


C# switch on type

&gt; **Possible Duplicate:**  
&gt; [JavaScript: Check if object is array?](https://stackoverflow.com/questions/4775722/javascript-check-if-object-is-array)  

&lt;!-- End of automatically inserted text --&gt;

Why is an array of objects considered an object, and not an array? For example:

    $.ajax({
        url: &#39;http://api.twitter.com/1/statuses/user_timeline.json&#39;,
        data: { screen_name: &#39;mick__romney&#39;},
        dataType: &#39;jsonp&#39;,
        success: function(data) {
            console.dir(data); //Array[20]
            alert(typeof data); //Object
        }
    });​

[Fiddle][1]


  [1]: http://jsfiddle.net/6JCcj/

Why does typeof array with objects return &quot;object&quot; and not &quot;array&quot;?

Why is `null` considered an `object` in JavaScript?

Is checking 

    if ( object == null )
          Do something

the same as 

    if ( !object )
          Do something

?

And also:

What is the difference between `null` and `undefined`?

Why is null an object and what&#39;s the difference between null and undefined?

In C++, how does one find the type of a variable?

How do I get the type of a variable?

Explain to me what `keyof typeof` means in TypeScript

Example:

    enum ColorsEnum {
        white = &#39;#ffffff&#39;,
        black = &#39;#000000&#39;,
    }
    
    type Colors = keyof typeof ColorsEnum;

The last row is equivalent to:

    type Colors = &quot;white&quot; | &quot;black&quot;

But how does it work?

I would expect `typeof ColorsEnum` to return something like `&quot;Object&quot;` and then `keyof &quot;Object&quot;` to not do anything interesting. But I am obviously wrong.

What does &quot;keyof typeof&quot; mean in TypeScript?

I am wondering what the difference is between `typeid` and `typeof` in C++. Here&#39;s what I know:

 - `typeid` is mentioned in the documentation for  [type_info][1] which is defined in the C++ header file [typeinfo][2].

 - `typeof` is defined in the GCC extension for C and in the C++ [Boost][3] library.

Also, here is test code test that I&#39;ve created where I&#39;ve discovered that `typeid` does not return what I expected. Why?

**main.cpp**

    #include &lt;iostream&gt;  
    #include &lt;typeinfo&gt;  //for &#39;typeid&#39; to work  
        
    class Person {  
        public:
        // ... Person members ...  
        virtual ~Person() {}  
    };  
        
    class Employee : public Person {  
        // ... Employee members ...  
    };  
        
    int main () {  
        Person person;  
        Employee employee;  
        Person *ptr = &amp;employee;  
        int t = 3;  
       
        std::cout &lt;&lt; typeid(t).name() &lt;&lt; std::endl;  
        std::cout &lt;&lt; typeid(person).name() &lt;&lt; std::endl;   // Person (statically known at compile-time)  
        std::cout &lt;&lt; typeid(employee).name() &lt;&lt; std::endl; // Employee (statically known at compile-time)  
        std::cout &lt;&lt; typeid(ptr).name() &lt;&lt; std::endl;      // Person * (statically known at compile-time)  
        std::cout &lt;&lt; typeid(*ptr).name() &lt;&lt; std::endl;     // Employee (looked up dynamically at run-time  
                                                           // because it is the dereference of a pointer
                                                           // to a polymorphic class)  
     }  

**output:**

&lt;!-- language: none --&gt;

    bash-3.2$ g++ -Wall main.cpp -o main  
    bash-3.2$ ./main   
    i  
    6Person  
    8Employee  
    P6Person  
    8Employee

  [1]: http://www.cplusplus.com/reference/typeinfo/type_info/
  [2]: http://www.cplusplus.com/reference/typeinfo/?kw=typeinfo
  [3]: http://en.wikipedia.org/wiki/Boost_C%2B%2B_Libraries

&#39;typeid&#39; versus &#39;typeof&#39; in C++

Is there anyway to detect if a JavaScript object is a regex?

For example, I would like to do something like this:

    var t = /^foo(bar)?$/i;
    alert(typeof t); //I want this to return &quot;regexp&quot;

Is this possible?

Thanks!

EDIT: Thanks for all the answers. It seems I have two very good choices:

    obj.constructor.name === &quot;RegExp&quot;

or

    obj instanceof RegExp

Any major pros/cons to either method?

Thanks again!

typeof for RegExp

I had a perception that, type of a lambda is a function pointer. When I performed following test, I found it to be wrong ([demo](http://ideone.com/5ZRRsA)).

    #define LAMBDA [] (int i) -&gt; long { return 0; }
    int main ()
    {
      long (*pFptr)(int) = LAMBDA;  // ok
      auto pAuto = LAMBDA;  // ok
      assert(typeid(pFptr) == typeid(pAuto));  // assertion fails !
    }
Is above code missing any point ? If not then, what is the `typeof` a lambda expression when deduced with `auto` keyword ?

What is the type of lambda when deduced with &quot;auto&quot; in C++11?

If I have:

    void MyMethod(Object obj) {   ...   }

How can I cast `obj` to what its actual type is?



How to cast Object to its actual type?

In R, I&#39;d like to retrieve a list of global variables at the end of my script and iterate over them. Here is my code

    #declare a few sample variables
    a&lt;-10
    b&lt;-&quot;Hello world&quot;
    c&lt;-data.frame()
    
    #get all global variables in script and iterate over them
    myGlobals&lt;-objects()
    for(i in myGlobals){
      print(typeof(i))     #prints &#39;character&#39;
    }

My problem is that `typeof(i)` always returns `character` even though variable `a` and `c` are not character variables. How can I get the original type of variable inside the for loop?

Get type of all variables

For example:

    int a = 12;
    cout &lt;&lt; typeof(a) &lt;&lt; endl;

Expected output:

    int

Is it possible to print a variable&#39;s type in standard C++?

Is there a simple way to determine if a variable is a list, dictionary, or something else? I am getting an object back that may be either type and I need to be able to tell the difference.


Determine the type of an object?

I need to test whether the value of a form&#39;s `onsubmit` is a function.  The format is typically `onsubmit=&quot;return valid();&quot;`.  Is there a way to tell if this is a function, and if it&#39;s callable?  Using typeof just returns that it&#39;s a string, which doesn&#39;t help me much.

**EDIT**: Of course, I understand that &quot;return valid();&quot; is a string.  I&#39;ve `replace`d it down to &quot;valid();&quot;, and even &quot;valid()&quot;.  I want to know if either of those is a function.

**EDIT**: Here&#39;s some code, which may help explain my problem:

    $(&quot;a.button&quot;).parents(&quot;form&quot;).submit(function() {
        var submit_function = $(&quot;a.button&quot;).parents(&quot;form&quot;).attr(&quot;onsubmit&quot;);
        if ( submit_function &amp;&amp; typeof( submit_function.replace(/return /,&quot;&quot;) ) == &#39;function&#39; ) {
            return eval(submit_function.replace(/return /,&quot;&quot;));
        } else {
            alert(&quot;onSubmit is not a function.\n\nIs the script included?&quot;); return false;
        }
    } );

**EDIT 2**: Here&#39;s the new code.  It seems that I still have to use an eval, because calling form.submit() doesn&#39;t fire existing onsubmits.

    var formObj = $(&quot;a.button&quot;).parents(&quot;form&quot;);
    formObj.submit(function() {
        if ( formObj[0].onsubmit &amp;&amp; typeof( formObj.onsubmit ) == &#39;function&#39; ) {
            return eval(formObj.attr(&quot;onsubmit&quot;).replace(/return /,&quot;&quot;));
        } else {
            alert(&quot;onSubmit is not a function.\n\nIs the script included?&quot;);
            return false;
        }
    } );

Suggestions on possibly how to do this better?

Testing if value is a function

I&#39;m a Java newbie. I&#39;m trying to figure out whether a number is a Double with something like this:

    if ( typeof ( items.elementAt(1) )== Double ) {
           sum.add( i, items.elementAt(1));
    }

Would appreciate if someone could tell me how to rearrange the syntax to make this work properly.


Figuring out whether a number is a Double in Java

In my particular case:

    callback instanceof Function

or 

    typeof callback == &quot;function&quot;

does it even matter, what&#39;s the difference?

**Additional Resource:**

JavaScript-Garden [typeof][1] vs [instanceof][2]


  [1]: http://bonsaiden.github.com/JavaScript-Garden/#types.typeof
  [2]: http://bonsaiden.github.com/JavaScript-Garden/#types.instanceof

What is the difference between typeof and instanceof and when should one be used vs. the other?

How should I detect if the argument is an array because `typeof []` returns `&#39;object&#39;` and I want to distinguish between arrays and objects.

It is possible that object will look like `{&quot;0&quot;:&quot;string&quot;,&quot;1&quot;:&quot;string&quot;,&quot;length&quot;:&quot;2&quot;}` but I don&#39;t want it to come out as an array if it is in fact an object looking like an array.

`JSON.parse` and `JSON.stringify` are able to make this distinction. How can I do it?

I am using Node.JS which is based on V8 the same as Chrome.

JavaScript: detect if argument is array instead of object (Node.JS)

I&#39;ve seen many people use the following code:

    Type t = typeof(obj1);
    if (t == typeof(int))
        // Some code here

But I know you could also do this:

    if (obj1.GetType() == typeof(int))
        // Some code here

Or this:

    if (obj1 is int)
        // Some code here



Personally, I feel the last one is the cleanest, but is there something I&#39;m missing? Which one is the best to use, or is it personal preference?

Type Checking: typeof, GetType, or is?

Why this works

    if (mycontrol.GetType() == typeof(TextBox))
    {} 

and this do not?

    Type tp = typeof(mycontrol);

But this works

    Type tp = mycontrol.GetType();

I myself use `is` operator for checking type but my understanding fails when I use `typeof()` and `GetType()`

Where and when to use `GetType()` or `typeof()`?

When and where to use GetType() or typeof()?

Getting the classname of an object as `String` using:

    object_getClassName(myViewController)

returns something like this:

    _TtC5AppName22CalendarViewController

I am looking for the *pure* version: `&quot;CalendarViewController&quot;`. How do I get a *cleaned up* string of the class name instead? 

I found some attempts of questions about this but not an actual answer. Is it not possible at all?

Get class name of object as string in Swift

Is typeof in C, really an operator?  
I&#39;m thinking because there is no polymorphism in C, that there is nothing to do at run-time.  That is, the answer to typeof is known at compile-time.  (I can&#39;t think of a use of typeof that would not be known at compile time.) So it appears to be more of a compile-time directive, than an operator.  

Does typeof use any (processor) run-time (in GCC)?

typeof operator in C

Is there any way to efficiently check if the variable is Object or Array, in NodeJS &amp; V8? 

I&#39;m writing a Model for MongoDB and NodeJS, and to traverse the object tree I need to know if the object is simple (Number, String, ...) or composite (Hash, Array).

It seems that V8 has fast built-in `Array.isArray`, but how to check if object is an Object? I mean complex object like hash `{}` or instance of class, not something like `new String()`?

Usually it may be done as this:

    Object.prototype.toString.call(object) == &quot;[object Object]&quot;

or this:

    object === Object(object)

But it seems that this operations aren&#39;t cheap, maybe there&#39;s some more efficient? It&#39;s ok if it&#39;s not universal and doesn&#39;t works on all engines, I need it only to work on V8.

How to efficiently check if variable is Array or Object (in NodeJS &amp; V8)?

I have the following code:

   

    return &quot;[Inserted new &quot; + typeof(T).ToString() + &quot;]&quot;;

But

     typeof(T).ToString()

  returns the full name including namespace

Is there anyway to just get the class name (without any namespace qualifiers?)

Get type name without full namespace

Is there any difference between `typeof (myVariable)` compared to `typeof myVariable`? 

Both work, but coming from PHP, I don&#39;t understand why this function can use parenthesis or not. 



Why does &quot;typeof&quot; not need parentheses?

According to [MDN&#39;s documentation on `undefined`][1]:

&gt; In modern browsers (JavaScript 1.8.5 / Firefox 4+), undefined is a non-configurable, non-writable property per the ECMAScript 5 specification. Even when this is not the case, avoid overriding it.

One of the property attributes of *undefined* is that is not writable.

But if I do:

&lt;!-- begin snippet: js hide: false console: true babel: false --&gt;

&lt;!-- language: lang-js --&gt;

    var undefined = &#39;hello&#39;;
    var test = undefined;
    console.log(typeof test);
    //string

&lt;!-- end snippet --&gt;

Does that mean that I can overwrite the value of `undefined`? What happens if someone does that? Should JavaScript warn about that?

  [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined







All Typeof Solutions on Gang of Coders

Total of 27 Typeof Solutions

_.isFunction(a) vs. typeof a === 'function'? javascript

Better way to get type of a Javascript variable?

How to determine the primitive type of a primitive variable?

C# switch on type

Why does typeof array with objects return "object" and not "array"?

Why is null an object and what's the difference between null and undefined?

How do I get the type of a variable?

What does "keyof typeof" mean in TypeScript?

'typeid' versus 'typeof' in C++