Get the name of an object s type

Question

Is there a JavaScript equivalent of Java s class getName

User · Answer

Use constructor name when you can  and regex function when I can t   Function prototype getName   function      if  typeof this name     undefined       return this name    else     return  function         exec this toString    1

User · Answer

Here is an implementation based on the accepted answer    x000D   x000D      x000D     Returns the name of an object s type  x000D     x000D     If the input is undefined  returns  Undefined   x000D     If the input is null  returns  Null   x000D     If the input is a boolean  returns  Boolean   x000D     If the input is a number  returns  Number   x000D     If the input is a string  returns  String   x000D     If the input is a named function or a class constructor  returns  Function   x000D     If the input is an anonymous function  returns  AnonymousFunction   x000D     If the input is an arrow function  returns  ArrowFunction   x000D     If the input is a class instance  returns  Object   x000D     x000D      param  Object  object an object x000D      return  String  the name of the object s class x000D      see  lt a href  https   stackoverflow com a 332429 14731  gt https   stackoverflow com a 332429 14731 lt  a gt  x000D      see getFunctionName x000D      see getObjectClass  x000D      x000D  function getTypeName object  x000D    x000D    const objectToString   Object prototype toString call object  slice 8  -1   x000D    if  objectToString      Function   x000D      x000D      const instanceToString   object toString    x000D      if  instanceToString indexOf     gt        -1  x000D        return  ArrowFunction   x000D      const getFunctionName     function             x000D      const match   instanceToString match getFunctionName   x000D      if  match     null  x000D        return  AnonymousFunction   x000D      return  Function   x000D      x000D       Built-in types  e g  String  or class instances x000D    return objectToString  x000D     x000D   x000D      x000D     Returns the name of a function  x000D     x000D     If the input is an anonymous function  returns     x000D     If the input is an arrow function  returns    gt    x000D     x000D      param  Function  fn a function x000D      return  String  the name of the function x000D      throws  TypeError  if   code fn  is not a function x000D      see getTypeName x000D      x000D  function getFunctionName fn  x000D    x000D    try x000D      x000D      const instanceToString   fn toString    x000D      if  instanceToString indexOf     gt        -1  x000D        return    gt    x000D      const getFunctionName     function             x000D      const match   instanceToString match getFunctionName   x000D      if  match     null  x000D        x000D        const objectToString   Object prototype toString call fn  slice 8  -1   x000D        if  objectToString      Function   x000D          return     x000D        throw TypeError  object must be a Function  n    x000D           Actual      getTypeName fn    x000D        x000D      return match 1   x000D      x000D    catch  e  x000D      x000D      throw TypeError  object must be a Function  n    x000D         Actual      getTypeName fn    x000D      x000D     x000D   x000D      x000D      param  Object  object an object x000D      return  String  the name of the object s class x000D      throws  TypeError  if   code object  is not an Object x000D      see getTypeName x000D      x000D  function getObjectClass object  x000D    x000D    const getFunctionName     function             x000D    const result   object constructor toString   match getFunctionName  1   x000D    if  result      Function   x000D      x000D      throw TypeError  object must be an Object  n    x000D         Actual      getTypeName object    x000D      x000D    return result  x000D     x000D   x000D   x000D  function UserFunction   x000D    x000D    x000D   x000D  function UserClass   x000D    x000D    x000D   x000D  let anonymousFunction   function   x000D    x000D     x000D   x000D  let arrowFunction   i   gt  i   1  x000D   x000D  console log  getTypeName undefined       getTypeName undefined    x000D  console log  getTypeName null       getTypeName null    x000D  console log  getTypeName true       getTypeName true    x000D  console log  getTypeName 5       getTypeName 5    x000D  console log  getTypeName   text         getTypeName  text     x000D  console log  getTypeName userFunction       getTypeName UserFunction    x000D  console log  getFunctionName userFunction       getFunctionName UserFunction    x000D  console log  getTypeName anonymousFunction       getTypeName anonymousFunction    x000D  console log  getFunctionName anonymousFunction       getFunctionName anonymousFunction    x000D  console log  getTypeName arrowFunction       getTypeName arrowFunction    x000D  console log  getFunctionName arrowFunction       getFunctionName arrowFunction    x000D    console log  getFunctionName userClass       getFunctionName new UserClass      x000D  console log  getTypeName userClass       getTypeName new UserClass      x000D  console log  getObjectClass userClass       getObjectClass new UserClass      x000D    console log  getObjectClass userFunction       getObjectClass UserFunction    x000D    console log  getObjectClass userFunction       getObjectClass anonymousFunction    x000D    console log  getObjectClass arrowFunction       getObjectClass arrowFunction    x000D  console log  getTypeName nativeObject       getTypeName navigator mediaDevices getUserMedia    x000D  console log  getFunctionName nativeObject       getFunctionName navigator mediaDevices getUserMedia    x000D   x000D   x000D    We only use the constructor property when we have no other choice

User · Answer

Lodash has many isMethods so if you re using Lodash maybe a mixin like this can be useful        Mixin for identifying a Javascript Object      mixin          identify    function object            var output            var isMethods     isArguments    isArray    isArguments    isBoolean    isDate    isArguments                   isElement    isError    isFunction    isNaN    isNull    isNumber                   isPlainObject    isRegExp    isString    isTypedArray    isUndefined    isEmpty    isObject              this each isMethods  function  method                  if  this method  object                     output   method                  return false                              bind this          return output                  It adds a method to lodash called  identify  which works as follow   console log   identify  hello friend              isString   Plunker  http   plnkr co edit Zdr0KDtQt76Ul3KTEDSN

User · Answer

You can use the  instanceof  operator to determine if an object is an instance of a certain class or not  If you do not know the name of an object s type  you can use its constructor property  The constructor property of objects  is a reference to the function that is used to initialize them  Example   function Circle  x y radius        this  x   x      this  y   y      this  radius   raduius    var c1   new Circle 10 20 5     Now c1 constructor is a reference to the Circle   function  You can alsow use the typeof operator  but the typeof operator shows limited information  One solution is to use the toString   method of the Object global object  For example if you have an object  say myObject  you can use the toString   method of the global Object to determine the type of the class of myObject  Use this   Object prototype toString apply myObject

User · Answer

Jason Bunting s answer gave me enough of a clue to find what I needed    lt  lt Object instance gt  gt  constructor name   So  for example  in the following piece of code   function MyObject      var myInstance   new MyObject      myInstance constructor name would return  MyObject

User · Answer

Lodash has many isMethods so if you re using Lodash maybe a mixin like this can be useful        Mixin for identifying a Javascript Object      mixin          identify    function object            var output            var isMethods     isArguments    isArray    isArguments    isBoolean    isDate    isArguments                   isElement    isError    isFunction    isNaN    isNull    isNumber                   isPlainObject    isRegExp    isString    isTypedArray    isUndefined    isEmpty    isObject              this each isMethods  function  method                  if  this method  object                     output   method                  return false                              bind this          return output                  It adds a method to lodash called  identify  which works as follow   console log   identify  hello friend              isString   Plunker  http   plnkr co edit Zdr0KDtQt76Ul3KTEDSN

User · Answer

Here is an implementation based on the accepted answer    x000D   x000D      x000D     Returns the name of an object s type  x000D     x000D     If the input is undefined  returns  Undefined   x000D     If the input is null  returns  Null   x000D     If the input is a boolean  returns  Boolean   x000D     If the input is a number  returns  Number   x000D     If the input is a string  returns  String   x000D     If the input is a named function or a class constructor  returns  Function   x000D     If the input is an anonymous function  returns  AnonymousFunction   x000D     If the input is an arrow function  returns  ArrowFunction   x000D     If the input is a class instance  returns  Object   x000D     x000D      param  Object  object an object x000D      return  String  the name of the object s class x000D      see  lt a href  https   stackoverflow com a 332429 14731  gt https   stackoverflow com a 332429 14731 lt  a gt  x000D      see getFunctionName x000D      see getObjectClass  x000D      x000D  function getTypeName object  x000D    x000D    const objectToString   Object prototype toString call object  slice 8  -1   x000D    if  objectToString      Function   x000D      x000D      const instanceToString   object toString    x000D      if  instanceToString indexOf     gt        -1  x000D        return  ArrowFunction   x000D      const getFunctionName     function             x000D      const match   instanceToString match getFunctionName   x000D      if  match     null  x000D        return  AnonymousFunction   x000D      return  Function   x000D      x000D       Built-in types  e g  String  or class instances x000D    return objectToString  x000D     x000D   x000D      x000D     Returns the name of a function  x000D     x000D     If the input is an anonymous function  returns     x000D     If the input is an arrow function  returns    gt    x000D     x000D      param  Function  fn a function x000D      return  String  the name of the function x000D      throws  TypeError  if   code fn  is not a function x000D      see getTypeName x000D      x000D  function getFunctionName fn  x000D    x000D    try x000D      x000D      const instanceToString   fn toString    x000D      if  instanceToString indexOf     gt        -1  x000D        return    gt    x000D      const getFunctionName     function             x000D      const match   instanceToString match getFunctionName   x000D      if  match     null  x000D        x000D        const objectToString   Object prototype toString call fn  slice 8  -1   x000D        if  objectToString      Function   x000D          return     x000D        throw TypeError  object must be a Function  n    x000D           Actual      getTypeName fn    x000D        x000D      return match 1   x000D      x000D    catch  e  x000D      x000D      throw TypeError  object must be a Function  n    x000D         Actual      getTypeName fn    x000D      x000D     x000D   x000D      x000D      param  Object  object an object x000D      return  String  the name of the object s class x000D      throws  TypeError  if   code object  is not an Object x000D      see getTypeName x000D      x000D  function getObjectClass object  x000D    x000D    const getFunctionName     function             x000D    const result   object constructor toString   match getFunctionName  1   x000D    if  result      Function   x000D      x000D      throw TypeError  object must be an Object  n    x000D         Actual      getTypeName object    x000D      x000D    return result  x000D     x000D   x000D   x000D  function UserFunction   x000D    x000D    x000D   x000D  function UserClass   x000D    x000D    x000D   x000D  let anonymousFunction   function   x000D    x000D     x000D   x000D  let arrowFunction   i   gt  i   1  x000D   x000D  console log  getTypeName undefined       getTypeName undefined    x000D  console log  getTypeName null       getTypeName null    x000D  console log  getTypeName true       getTypeName true    x000D  console log  getTypeName 5       getTypeName 5    x000D  console log  getTypeName   text         getTypeName  text     x000D  console log  getTypeName userFunction       getTypeName UserFunction    x000D  console log  getFunctionName userFunction       getFunctionName UserFunction    x000D  console log  getTypeName anonymousFunction       getTypeName anonymousFunction    x000D  console log  getFunctionName anonymousFunction       getFunctionName anonymousFunction    x000D  console log  getTypeName arrowFunction       getTypeName arrowFunction    x000D  console log  getFunctionName arrowFunction       getFunctionName arrowFunction    x000D    console log  getFunctionName userClass       getFunctionName new UserClass      x000D  console log  getTypeName userClass       getTypeName new UserClass      x000D  console log  getObjectClass userClass       getObjectClass new UserClass      x000D    console log  getObjectClass userFunction       getObjectClass UserFunction    x000D    console log  getObjectClass userFunction       getObjectClass anonymousFunction    x000D    console log  getObjectClass arrowFunction       getObjectClass arrowFunction    x000D  console log  getTypeName nativeObject       getTypeName navigator mediaDevices getUserMedia    x000D  console log  getFunctionName nativeObject       getFunctionName navigator mediaDevices getUserMedia    x000D   x000D   x000D    We only use the constructor property when we have no other choice

User · Answer

Jason Bunting s answer gave me enough of a clue to find what I needed    lt  lt Object instance gt  gt  constructor name   So  for example  in the following piece of code   function MyObject      var myInstance   new MyObject      myInstance constructor name would return  MyObject

User · Answer

Jason Bunting s answer gave me enough of a clue to find what I needed    lt  lt Object instance gt  gt  constructor name   So  for example  in the following piece of code   function MyObject      var myInstance   new MyObject      myInstance constructor name would return  MyObject

User · Answer

You can use the instanceof operator to see if an object is an instance of another  but since there are no classes  you can t get a class name

User · Answer

Use constructor name when you can  and regex function when I can t   Function prototype getName   function      if  typeof this name     undefined       return this name    else     return  function         exec this toString    1

User · Answer

You can use the  instanceof  operator to determine if an object is an instance of a certain class or not  If you do not know the name of an object s type  you can use its constructor property  The constructor property of objects  is a reference to the function that is used to initialize them  Example   function Circle  x y radius        this  x   x      this  y   y      this  radius   raduius    var c1   new Circle 10 20 5     Now c1 constructor is a reference to the Circle   function  You can alsow use the typeof operator  but the typeof operator shows limited information  One solution is to use the toString   method of the Object global object  For example if you have an object  say myObject  you can use the toString   method of the global Object to determine the type of the class of myObject  Use this   Object prototype toString apply myObject

User · Answer

I was actually looking for a similar thing and came across this question  Here is how I get types  jsfiddle  var TypeOf   function   thing          var typeOfThing   typeof thing       if    object      typeOfThing              typeOfThing   Object prototype toString call  thing             if     object Object       typeOfThing                  if   thing constructor name                     return thing constructor name                              else if           thing constructor toString   charAt 0                      typeOfThing   typeOfThing substring  8 typeOfThing length - 1                                else                    typeOfThing   thing constructor toString   match   function s   w                        if   typeOfThing                          return typeOfThing 1                                       else                       return  Function                                                       else               typeOfThing   typeOfThing substring  8 typeOfThing length - 1                         return typeOfThing charAt 0  toUpperCase     typeOfThing slice 1

User · Answer

Use class name  This also works with function name   class TestA    console log TestA name       TestA   function TestB      console log TestB name       TestB

User · Answer

The kind   function from Agave JS will return    the closest prototype in the inheritance tree for always-primitive types like  null  and  undefined   the primitive name     It works on all JS objects and primitives  regardless of how they were created  and doesn t have any surprises  Examples   Numbers  kind 37       Number  kind 3 14       Number  kind Math LN2       Number  kind Infinity       Number  kind Number 1        Number  kind new Number 1        Number    NaN  kind NaN       NaN    Strings  kind          String  kind  bla        String  kind String  abc         String  kind new String  abc         String    Booleans  kind true       Boolean  kind false       Boolean  kind new Boolean true        Boolean    Arrays  kind  1  2  4        Array  kind new Array 1  2  3        Array    Objects  kind  a 1        Object  kind new Object         Object    Dates  kind new Date         Date    Functions  kind function           Function  kind new Function  console log arguments          Function  kind Math sin       Function    undefined  kind undefined       undefined    null  kind null       null

User · Answer

Is there a JavaScript equivalent of Java s class getName     No  ES2015 Update  the name of class Foo    is Foo name   The name of thing s class  regardless of thing s type  is thing constructor name  Builtin constructors in an ES2015 environment have the correct name property  for instance  2  constructor name is  quot Number quot    But here are various hacks that all fall down in one way or another  Here is a hack that will do what you need - be aware that it modifies the Object s prototype  something people frown upon  usually for good reason  Object prototype getName   function         var funcNameRegex    function    1           var results    funcNameRegex  exec  this  constructor toString        return  results  amp  amp  results length  gt  1    results 1     quot  quot       Now  all of your objects will have the function  getName    that will return the name of the constructor as a string  I have tested this in FF3 and IE7  I can t speak for other implementations  If you don t want to do that  here is a discussion on the various ways of determining types in JavaScript     I recently updated this to be a bit more exhaustive  though it is hardly that  Corrections welcome    Using the constructor property    Every object has a value for its constructor property  but depending on how that object was constructed as well as what you want to do with that value  it may or may not be useful  Generally speaking  you can use the constructor property to test the type of the object like so  var myArray    1 2 3    myArray constructor    Array      true  So  that works well enough for most needs  That said    Caveats Will not work AT ALL in many cases This pattern  though broken  is quite common  function Thingy       Thingy prototype         method1  function                method2  function               Objects constructed via new Thingy will have a constructor property that points to Object  not Thingy  So we fall right at the outset  you simply cannot trust constructor in a codebase that you don t control  Multiple Inheritance An example where it isn t as obvious is using multiple inheritance  function a     this foo   1   function b     this bar   2    b prototype   new a       b inherits from a  Things now don t work as you might expect them to  var f   new b       instantiate a new object with the b constructor  f constructor    b      false  f constructor    a      true  So  you might get unexpected results if the object your testing has a different object set as its prototype  There are ways around this outside the scope of this discussion  There are other uses for the constructor property  some of them interesting  others not so much  for now we will not delve into those uses since it isn t relevant to this discussion  Will not work cross-frame and cross-window Using  constructor for type checking will break when you want to check the type of objects coming from different window objects  say that of an iframe or a popup window  This is because there s a different version of each core type constructor in each  window   i e  iframe contentWindow Array     Array    false   Using the instanceof operator    The instanceof operator is a clean way of testing object type as well  but has its own potential issues  just like the constructor property  var myArray    1 2 3    myArray instanceof Array      true  myArray instanceof Object      true  But instanceof fails to work for literal values  because literals are not Objects  3 instanceof Number    false  abc  instanceof String    false true instanceof Boolean    false  The literals need to be wrapped in an Object in order for instanceof to work  for example new Number 3  instanceof Number    true  The  constructor check works fine for literals because the   method invocation implicitly wraps the literals in their respective object type 3  constructor     Number    true  abc  constructor     String    true true constructor     Boolean    true  Why two dots for the 3  Because Javascript interprets the first dot as a decimal point    Will not work cross-frame and cross-window instanceof also will not work across different windows  for the same reason as the constructor property check   Using the name property of the constructor property    Does not work AT ALL in many cases Again  see above  it s quite common for constructor to be utterly and completely wrong and useless  Does NOT work in  lt IE9 Using myObjectInstance constructor name will give you a string containing the name of the constructor function used  but is subject to the caveats about the constructor property that were mentioned earlier  For IE9 and above  you can monkey-patch in support  if  Function prototype name     undefined  amp  amp  Object defineProperty     undefined        Object defineProperty Function prototype   name             get  function                 var funcNameRegex    function s     s     s                  var results    funcNameRegex  exec  this  toString                 return  results  amp  amp  results length  gt  1    results 1     quot  quot                      set  function value                Updated version from the article in question  This was added 3 months after the article was published  this is the recommended version to use by the article s author Matthew Scharley  This change was inspired by comments pointing out potential pitfalls in the previous code  if  Function prototype name     undefined  amp  amp  Object defineProperty     undefined        Object defineProperty Function prototype   name             get  function                 var funcNameRegex    function s      1                    var results    funcNameRegex  exec  this  toString                 return  results  amp  amp  results length  gt  1    results 1  trim      quot  quot                      set  function value                 Using Object prototype toString It turns out  as this post details  you can use Object prototype toString - the low level and generic implementation of toString - to get the type for all built-in types Object prototype toString call  abc       object String  Object prototype toString call  abc       object RegExp  Object prototype toString call  1 2 3       object Array   One could write a short helper function such as function type obj       return Object prototype toString call obj  slice 8  -1      to remove the cruft and get at just the type name type  abc      String  However  it will return Object for all user-defined types   Caveats for all    All of these are subject to one potential problem  and that is the question of how the object in question was constructed  Here are various ways of building objects and the values that the different methods of type checking will return     using a named function  function Foo     this a   1    var obj   new Foo     obj instanceof Object               true  obj instanceof Foo                  true  obj constructor    Foo              true  obj constructor name     quot Foo quot        true     let s add some prototypical inheritance function Bar     this b   2    Foo prototype   new Bar    obj   new Foo     obj instanceof Object               true  obj instanceof Foo                  true  obj constructor    Foo              false  obj constructor name     quot Foo quot        false      using an anonymous function  obj   new  function     this a   1         obj instanceof Object                   true  obj constructor    obj constructor      true  obj constructor name     quot  quot               true      using an anonymous function assigned to a variable var Foo   function     this a   1     obj   new Foo     obj instanceof Object           true  obj instanceof Foo              true  obj constructor    Foo          true  obj constructor name     quot  quot       true      using object literal syntax obj     foo   1     obj instanceof Object                 true  obj constructor    Object             true  obj constructor name     quot Object quot       true  While not all permutations are present in this set of examples  hopefully there are enough to provide you with an idea about how messy things might get depending on your needs  Don t assume anything  if you don t understand exactly what you are after  you may end up with code breaking where you don t expect it to because of a lack of grokking the subtleties  NOTE  Discussion of the typeof operator may appear to be a glaring omission  but it really isn t useful in helping to identify whether an object is a given type  since it is very simplistic  Understanding where typeof is useful is important  but I don t currently feel that it is terribly relevant to this discussion  My mind is open to change though

User · Answer

Use class name  This also works with function name   class TestA    console log TestA name       TestA   function TestB      console log TestB name       TestB

User · Answer

You can use the  instanceof  operator to determine if an object is an instance of a certain class or not  If you do not know the name of an object s type  you can use its constructor property  The constructor property of objects  is a reference to the function that is used to initialize them  Example   function Circle  x y radius        this  x   x      this  y   y      this  radius   raduius    var c1   new Circle 10 20 5     Now c1 constructor is a reference to the Circle   function  You can alsow use the typeof operator  but the typeof operator shows limited information  One solution is to use the toString   method of the Object global object  For example if you have an object  say myObject  you can use the toString   method of the global Object to determine the type of the class of myObject  Use this   Object prototype toString apply myObject

User · Answer

Fairly Simple    My favorite method to get type of anything in JS   function getType entity       var x   Object prototype toString call entity      return x split      1  split      0  toLowerCase        my favorite method to check type of anything in JS   function checkType entity  type       return getType entity      type

User · Answer

Ok  folks I ve been slowly building a catch all method for this over some years lol   The trick is to      Have a mechanism for creating classes    Have a mechanism for checking all user created classes  primitives and values created generated by native constructors    Have a mechanism for extending user created classes into new ones so that the above functionality permeates through your code application library etc     For an example  or to see how I dealt with the problem  look at the following code on github  https   github com elycruz sjljs blob master src sjl sjl js and search for   classOf     classOfIs    and or defineSubClass    without the backticks          As you can see I have some mechanisms in place to force classOf to always give me the classes constructors type name regardless of whether it is a primitive  a user defined class  a value created using a native constructor  Null  NaN  etc    For every single javascript value I will get it s unique type name from the classOf function   In addition I can pass in actual constructors into sjl classOfIs to check a value s type in addition to being able to pass in it s type name as well   So for example              Please forgive long namespaces   I had no idea on the impact until after using them for a while  they suck haha   var SomeCustomClass   sjl package stdlib Extendable extend       constructor  function SomeCustomClass                        HelloIterator   sjl ns stdlib Iterator extend       function HelloIterator                      methods here                        static props methods here              helloIt   new HelloIterator     sjl classOfIs new SomeCustomClass    SomeCustomClass      true      true  sjl classOfIs helloIt  HelloIterator      true      true   var someString    helloworld    sjl classOfIs someString  String      true      true   sjl classOfIs 99  Number      true     true  sjl classOf NaN       NaN      true  sjl classOf new Map         Map   sjl classOf new Set         Set   sjl classOfIs  1  2  4   Array      true      true      etc       Also optionally the type you want to check against could be the type s name sjl classOfIs   a    b    c     Array       true      true   sjl classOfIs helloIt   HelloIterator       true      true          If you are interested in reading more on how I use the setup mentioned above take a look at the repo  https   github com elycruz sjljs   Also books with content on the subject  -  JavaScript Patterns  by Stoyan Stefanov  -  Javascript - The Definitive Guide   by David Flanagan  - and many others    search le  web    Also you can quickly test the features I m talking about here   - http   sjljs elycruz com 0 5 18 tests for-browser   also the 0 5 18 path in the url has the sources from github on there minus the node modules and such    Happy Coding

User · Answer

The closest you can get is typeof  but it only returns  object  for any sort of custom type  For those  see Jason Bunting   Edit  Jason s deleted his post for some reason  so just use Object s constructor property

User · Answer

The closest you can get is typeof  but it only returns  object  for any sort of custom type  For those  see Jason Bunting   Edit  Jason s deleted his post for some reason  so just use Object s constructor property

User · Answer

The closest you can get is typeof  but it only returns  object  for any sort of custom type  For those  see Jason Bunting   Edit  Jason s deleted his post for some reason  so just use Object s constructor property

User · Answer

You can use the  instanceof  operator to determine if an object is an instance of a certain class or not  If you do not know the name of an object s type  you can use its constructor property  The constructor property of objects  is a reference to the function that is used to initialize them  Example   function Circle  x y radius        this  x   x      this  y   y      this  radius   raduius    var c1   new Circle 10 20 5     Now c1 constructor is a reference to the Circle   function  You can alsow use the typeof operator  but the typeof operator shows limited information  One solution is to use the toString   method of the Object global object  For example if you have an object  say myObject  you can use the toString   method of the global Object to determine the type of the class of myObject  Use this   Object prototype toString apply myObject

User · Answer

Here is a solution that I have come up with that solves the shortcomings of instanceof  It can check an object s types from cross-windows and cross-frames and doesn t have problems with primitive types   function getType o        return Object prototype toString call o  match     object s          1     function isInstance obj  type        var ret   false      isTypeAString   getType type      String       functionConstructor  i  l  typeArray  context      if   isTypeAString  amp  amp  getType type      Function             throw new TypeError  type argument must be a string or function              if  obj     undefined  amp  amp  obj     null  amp  amp  obj constructor              get the Function constructor         functionConstructor   obj constructor          while  functionConstructor    functionConstructor constructor                functionConstructor   functionConstructor constructor                      get the object s window         context   functionConstructor    Function   self   functionConstructor  return window                get the constructor for the type         if  isTypeAString                  type is a string so we ll build the context  window Array or window some Type              for  typeArray   type split       i   0  l   typeArray length  i  lt  l  amp  amp  context  i                      context   context typeArray i                            else                 type is a function so execute the function passing in the object s window               the return should be a constructor             context   type context                       check if the object is an instance of the constructor         if  context                ret   obj instanceof context              if   ret  amp  amp   type     Number     type     String     type     Boolean                      ret   obj constructor    context                                   return ret      isInstance requires two parameters  an object and a type  The real trick to how it works is that it checks if the object is from the same window and if not gets the object s window   Examples   isInstance      Array      true isInstance  some string    String      true isInstance new Object     Object      true  function Animal      function Dog      Dog prototype   new Animal     isInstance new Dog     Dog      true isInstance new Dog     Animal      true isInstance new Dog     Object      true isInstance new Animal     Dog      false   The type argument can also be a callback function which returns a constructor  The callback function will receive one parameter which is the window of the provided object   Examples      Arguments  type check var args    function         return arguments         isInstance args  function w        return w Function  return arguments constructor            true     NodeList  type check var nl   document getElementsByTagName        isInstance nl  function w        return w document getElementsByTagName  bs   constructor        true   One thing to keep in mind is that IE  lt  9 does not provide the constructor on all objects so the above test for NodeList would return false and also a isInstance alert   Function   would return false

User · Answer

Is there a JavaScript equivalent of Java s class getName     No  ES2015 Update  the name of class Foo    is Foo name   The name of thing s class  regardless of thing s type  is thing constructor name  Builtin constructors in an ES2015 environment have the correct name property  for instance  2  constructor name is  quot Number quot    But here are various hacks that all fall down in one way or another  Here is a hack that will do what you need - be aware that it modifies the Object s prototype  something people frown upon  usually for good reason  Object prototype getName   function         var funcNameRegex    function    1           var results    funcNameRegex  exec  this  constructor toString        return  results  amp  amp  results length  gt  1    results 1     quot  quot       Now  all of your objects will have the function  getName    that will return the name of the constructor as a string  I have tested this in FF3 and IE7  I can t speak for other implementations  If you don t want to do that  here is a discussion on the various ways of determining types in JavaScript     I recently updated this to be a bit more exhaustive  though it is hardly that  Corrections welcome    Using the constructor property    Every object has a value for its constructor property  but depending on how that object was constructed as well as what you want to do with that value  it may or may not be useful  Generally speaking  you can use the constructor property to test the type of the object like so  var myArray    1 2 3    myArray constructor    Array      true  So  that works well enough for most needs  That said    Caveats Will not work AT ALL in many cases This pattern  though broken  is quite common  function Thingy       Thingy prototype         method1  function                method2  function               Objects constructed via new Thingy will have a constructor property that points to Object  not Thingy  So we fall right at the outset  you simply cannot trust constructor in a codebase that you don t control  Multiple Inheritance An example where it isn t as obvious is using multiple inheritance  function a     this foo   1   function b     this bar   2    b prototype   new a       b inherits from a  Things now don t work as you might expect them to  var f   new b       instantiate a new object with the b constructor  f constructor    b      false  f constructor    a      true  So  you might get unexpected results if the object your testing has a different object set as its prototype  There are ways around this outside the scope of this discussion  There are other uses for the constructor property  some of them interesting  others not so much  for now we will not delve into those uses since it isn t relevant to this discussion  Will not work cross-frame and cross-window Using  constructor for type checking will break when you want to check the type of objects coming from different window objects  say that of an iframe or a popup window  This is because there s a different version of each core type constructor in each  window   i e  iframe contentWindow Array     Array    false   Using the instanceof operator    The instanceof operator is a clean way of testing object type as well  but has its own potential issues  just like the constructor property  var myArray    1 2 3    myArray instanceof Array      true  myArray instanceof Object      true  But instanceof fails to work for literal values  because literals are not Objects  3 instanceof Number    false  abc  instanceof String    false true instanceof Boolean    false  The literals need to be wrapped in an Object in order for instanceof to work  for example new Number 3  instanceof Number    true  The  constructor check works fine for literals because the   method invocation implicitly wraps the literals in their respective object type 3  constructor     Number    true  abc  constructor     String    true true constructor     Boolean    true  Why two dots for the 3  Because Javascript interprets the first dot as a decimal point    Will not work cross-frame and cross-window instanceof also will not work across different windows  for the same reason as the constructor property check   Using the name property of the constructor property    Does not work AT ALL in many cases Again  see above  it s quite common for constructor to be utterly and completely wrong and useless  Does NOT work in  lt IE9 Using myObjectInstance constructor name will give you a string containing the name of the constructor function used  but is subject to the caveats about the constructor property that were mentioned earlier  For IE9 and above  you can monkey-patch in support  if  Function prototype name     undefined  amp  amp  Object defineProperty     undefined        Object defineProperty Function prototype   name             get  function                 var funcNameRegex    function s     s     s                  var results    funcNameRegex  exec  this  toString                 return  results  amp  amp  results length  gt  1    results 1     quot  quot                      set  function value                Updated version from the article in question  This was added 3 months after the article was published  this is the recommended version to use by the article s author Matthew Scharley  This change was inspired by comments pointing out potential pitfalls in the previous code  if  Function prototype name     undefined  amp  amp  Object defineProperty     undefined        Object defineProperty Function prototype   name             get  function                 var funcNameRegex    function s      1                    var results    funcNameRegex  exec  this  toString                 return  results  amp  amp  results length  gt  1    results 1  trim      quot  quot                      set  function value                 Using Object prototype toString It turns out  as this post details  you can use Object prototype toString - the low level and generic implementation of toString - to get the type for all built-in types Object prototype toString call  abc       object String  Object prototype toString call  abc       object RegExp  Object prototype toString call  1 2 3       object Array   One could write a short helper function such as function type obj       return Object prototype toString call obj  slice 8  -1      to remove the cruft and get at just the type name type  abc      String  However  it will return Object for all user-defined types   Caveats for all    All of these are subject to one potential problem  and that is the question of how the object in question was constructed  Here are various ways of building objects and the values that the different methods of type checking will return     using a named function  function Foo     this a   1    var obj   new Foo     obj instanceof Object               true  obj instanceof Foo                  true  obj constructor    Foo              true  obj constructor name     quot Foo quot        true     let s add some prototypical inheritance function Bar     this b   2    Foo prototype   new Bar    obj   new Foo     obj instanceof Object               true  obj instanceof Foo                  true  obj constructor    Foo              false  obj constructor name     quot Foo quot        false      using an anonymous function  obj   new  function     this a   1         obj instanceof Object                   true  obj constructor    obj constructor      true  obj constructor name     quot  quot               true      using an anonymous function assigned to a variable var Foo   function     this a   1     obj   new Foo     obj instanceof Object           true  obj instanceof Foo              true  obj constructor    Foo          true  obj constructor name     quot  quot       true      using object literal syntax obj     foo   1     obj instanceof Object                 true  obj constructor    Object             true  obj constructor name     quot Object quot       true  While not all permutations are present in this set of examples  hopefully there are enough to provide you with an idea about how messy things might get depending on your needs  Don t assume anything  if you don t understand exactly what you are after  you may end up with code breaking where you don t expect it to because of a lack of grokking the subtleties  NOTE  Discussion of the typeof operator may appear to be a glaring omission  but it really isn t useful in helping to identify whether an object is a given type  since it is very simplistic  Understanding where typeof is useful is important  but I don t currently feel that it is terribly relevant to this discussion  My mind is open to change though

User · Answer

The closest you can get is typeof  but it only returns  object  for any sort of custom type  For those  see Jason Bunting   Edit  Jason s deleted his post for some reason  so just use Object s constructor property

User · Answer

Jason Bunting s answer gave me enough of a clue to find what I needed    lt  lt Object instance gt  gt  constructor name   So  for example  in the following piece of code   function MyObject      var myInstance   new MyObject      myInstance constructor name would return  MyObject

User · Answer

Ok  folks I ve been slowly building a catch all method for this over some years lol   The trick is to      Have a mechanism for creating classes    Have a mechanism for checking all user created classes  primitives and values created generated by native constructors    Have a mechanism for extending user created classes into new ones so that the above functionality permeates through your code application library etc     For an example  or to see how I dealt with the problem  look at the following code on github  https   github com elycruz sjljs blob master src sjl sjl js and search for   classOf     classOfIs    and or defineSubClass    without the backticks          As you can see I have some mechanisms in place to force classOf to always give me the classes constructors type name regardless of whether it is a primitive  a user defined class  a value created using a native constructor  Null  NaN  etc    For every single javascript value I will get it s unique type name from the classOf function   In addition I can pass in actual constructors into sjl classOfIs to check a value s type in addition to being able to pass in it s type name as well   So for example              Please forgive long namespaces   I had no idea on the impact until after using them for a while  they suck haha   var SomeCustomClass   sjl package stdlib Extendable extend       constructor  function SomeCustomClass                        HelloIterator   sjl ns stdlib Iterator extend       function HelloIterator                      methods here                        static props methods here              helloIt   new HelloIterator     sjl classOfIs new SomeCustomClass    SomeCustomClass      true      true  sjl classOfIs helloIt  HelloIterator      true      true   var someString    helloworld    sjl classOfIs someString  String      true      true   sjl classOfIs 99  Number      true     true  sjl classOf NaN       NaN      true  sjl classOf new Map         Map   sjl classOf new Set         Set   sjl classOfIs  1  2  4   Array      true      true      etc       Also optionally the type you want to check against could be the type s name sjl classOfIs   a    b    c     Array       true      true   sjl classOfIs helloIt   HelloIterator       true      true          If you are interested in reading more on how I use the setup mentioned above take a look at the repo  https   github com elycruz sjljs   Also books with content on the subject  -  JavaScript Patterns  by Stoyan Stefanov  -  Javascript - The Definitive Guide   by David Flanagan  - and many others    search le  web    Also you can quickly test the features I m talking about here   - http   sjljs elycruz com 0 5 18 tests for-browser   also the 0 5 18 path in the url has the sources from github on there minus the node modules and such    Happy Coding

User · Answer

You can use the instanceof operator to see if an object is an instance of another  but since there are no classes  you can t get a class name

User · Answer

Here is a solution that I have come up with that solves the shortcomings of instanceof  It can check an object s types from cross-windows and cross-frames and doesn t have problems with primitive types   function getType o        return Object prototype toString call o  match     object s          1     function isInstance obj  type        var ret   false      isTypeAString   getType type      String       functionConstructor  i  l  typeArray  context      if   isTypeAString  amp  amp  getType type      Function             throw new TypeError  type argument must be a string or function              if  obj     undefined  amp  amp  obj     null  amp  amp  obj constructor              get the Function constructor         functionConstructor   obj constructor          while  functionConstructor    functionConstructor constructor                functionConstructor   functionConstructor constructor                      get the object s window         context   functionConstructor    Function   self   functionConstructor  return window                get the constructor for the type         if  isTypeAString                  type is a string so we ll build the context  window Array or window some Type              for  typeArray   type split       i   0  l   typeArray length  i  lt  l  amp  amp  context  i                      context   context typeArray i                            else                 type is a function so execute the function passing in the object s window               the return should be a constructor             context   type context                       check if the object is an instance of the constructor         if  context                ret   obj instanceof context              if   ret  amp  amp   type     Number     type     String     type     Boolean                      ret   obj constructor    context                                   return ret      isInstance requires two parameters  an object and a type  The real trick to how it works is that it checks if the object is from the same window and if not gets the object s window   Examples   isInstance      Array      true isInstance  some string    String      true isInstance new Object     Object      true  function Animal      function Dog      Dog prototype   new Animal     isInstance new Dog     Dog      true isInstance new Dog     Animal      true isInstance new Dog     Object      true isInstance new Animal     Dog      false   The type argument can also be a callback function which returns a constructor  The callback function will receive one parameter which is the window of the provided object   Examples      Arguments  type check var args    function         return arguments         isInstance args  function w        return w Function  return arguments constructor            true     NodeList  type check var nl   document getElementsByTagName        isInstance nl  function w        return w document getElementsByTagName  bs   constructor        true   One thing to keep in mind is that IE  lt  9 does not provide the constructor on all objects so the above test for NodeList would return false and also a isInstance alert   Function   would return false

User · Answer

Is there a JavaScript equivalent of Java s class getName     No  ES2015 Update  the name of class Foo    is Foo name   The name of thing s class  regardless of thing s type  is thing constructor name  Builtin constructors in an ES2015 environment have the correct name property  for instance  2  constructor name is  quot Number quot    But here are various hacks that all fall down in one way or another  Here is a hack that will do what you need - be aware that it modifies the Object s prototype  something people frown upon  usually for good reason  Object prototype getName   function         var funcNameRegex    function    1           var results    funcNameRegex  exec  this  constructor toString        return  results  amp  amp  results length  gt  1    results 1     quot  quot       Now  all of your objects will have the function  getName    that will return the name of the constructor as a string  I have tested this in FF3 and IE7  I can t speak for other implementations  If you don t want to do that  here is a discussion on the various ways of determining types in JavaScript     I recently updated this to be a bit more exhaustive  though it is hardly that  Corrections welcome    Using the constructor property    Every object has a value for its constructor property  but depending on how that object was constructed as well as what you want to do with that value  it may or may not be useful  Generally speaking  you can use the constructor property to test the type of the object like so  var myArray    1 2 3    myArray constructor    Array      true  So  that works well enough for most needs  That said    Caveats Will not work AT ALL in many cases This pattern  though broken  is quite common  function Thingy       Thingy prototype         method1  function                method2  function               Objects constructed via new Thingy will have a constructor property that points to Object  not Thingy  So we fall right at the outset  you simply cannot trust constructor in a codebase that you don t control  Multiple Inheritance An example where it isn t as obvious is using multiple inheritance  function a     this foo   1   function b     this bar   2    b prototype   new a       b inherits from a  Things now don t work as you might expect them to  var f   new b       instantiate a new object with the b constructor  f constructor    b      false  f constructor    a      true  So  you might get unexpected results if the object your testing has a different object set as its prototype  There are ways around this outside the scope of this discussion  There are other uses for the constructor property  some of them interesting  others not so much  for now we will not delve into those uses since it isn t relevant to this discussion  Will not work cross-frame and cross-window Using  constructor for type checking will break when you want to check the type of objects coming from different window objects  say that of an iframe or a popup window  This is because there s a different version of each core type constructor in each  window   i e  iframe contentWindow Array     Array    false   Using the instanceof operator    The instanceof operator is a clean way of testing object type as well  but has its own potential issues  just like the constructor property  var myArray    1 2 3    myArray instanceof Array      true  myArray instanceof Object      true  But instanceof fails to work for literal values  because literals are not Objects  3 instanceof Number    false  abc  instanceof String    false true instanceof Boolean    false  The literals need to be wrapped in an Object in order for instanceof to work  for example new Number 3  instanceof Number    true  The  constructor check works fine for literals because the   method invocation implicitly wraps the literals in their respective object type 3  constructor     Number    true  abc  constructor     String    true true constructor     Boolean    true  Why two dots for the 3  Because Javascript interprets the first dot as a decimal point    Will not work cross-frame and cross-window instanceof also will not work across different windows  for the same reason as the constructor property check   Using the name property of the constructor property    Does not work AT ALL in many cases Again  see above  it s quite common for constructor to be utterly and completely wrong and useless  Does NOT work in  lt IE9 Using myObjectInstance constructor name will give you a string containing the name of the constructor function used  but is subject to the caveats about the constructor property that were mentioned earlier  For IE9 and above  you can monkey-patch in support  if  Function prototype name     undefined  amp  amp  Object defineProperty     undefined        Object defineProperty Function prototype   name             get  function                 var funcNameRegex    function s     s     s                  var results    funcNameRegex  exec  this  toString                 return  results  amp  amp  results length  gt  1    results 1     quot  quot                      set  function value                Updated version from the article in question  This was added 3 months after the article was published  this is the recommended version to use by the article s author Matthew Scharley  This change was inspired by comments pointing out potential pitfalls in the previous code  if  Function prototype name     undefined  amp  amp  Object defineProperty     undefined        Object defineProperty Function prototype   name             get  function                 var funcNameRegex    function s      1                    var results    funcNameRegex  exec  this  toString                 return  results  amp  amp  results length  gt  1    results 1  trim      quot  quot                      set  function value                 Using Object prototype toString It turns out  as this post details  you can use Object prototype toString - the low level and generic implementation of toString - to get the type for all built-in types Object prototype toString call  abc       object String  Object prototype toString call  abc       object RegExp  Object prototype toString call  1 2 3       object Array   One could write a short helper function such as function type obj       return Object prototype toString call obj  slice 8  -1      to remove the cruft and get at just the type name type  abc      String  However  it will return Object for all user-defined types   Caveats for all    All of these are subject to one potential problem  and that is the question of how the object in question was constructed  Here are various ways of building objects and the values that the different methods of type checking will return     using a named function  function Foo     this a   1    var obj   new Foo     obj instanceof Object               true  obj instanceof Foo                  true  obj constructor    Foo              true  obj constructor name     quot Foo quot        true     let s add some prototypical inheritance function Bar     this b   2    Foo prototype   new Bar    obj   new Foo     obj instanceof Object               true  obj instanceof Foo                  true  obj constructor    Foo              false  obj constructor name     quot Foo quot        false      using an anonymous function  obj   new  function     this a   1         obj instanceof Object                   true  obj constructor    obj constructor      true  obj constructor name     quot  quot               true      using an anonymous function assigned to a variable var Foo   function     this a   1     obj   new Foo     obj instanceof Object           true  obj instanceof Foo              true  obj constructor    Foo          true  obj constructor name     quot  quot       true      using object literal syntax obj     foo   1     obj instanceof Object                 true  obj constructor    Object             true  obj constructor name     quot Object quot       true  While not all permutations are present in this set of examples  hopefully there are enough to provide you with an idea about how messy things might get depending on your needs  Don t assume anything  if you don t understand exactly what you are after  you may end up with code breaking where you don t expect it to because of a lack of grokking the subtleties  NOTE  Discussion of the typeof operator may appear to be a glaring omission  but it really isn t useful in helping to identify whether an object is a given type  since it is very simplistic  Understanding where typeof is useful is important  but I don t currently feel that it is terribly relevant to this discussion  My mind is open to change though

User · Answer

A little trick I use   function Square        this className    Square       this corners   4     var MySquare   new Square    console log MySquare className       Square

User · Answer

Using Object prototype toString  It turns out  as this post details  you can use Object prototype toString - the low level and generic implementation of toString - to get the type for all built-in types  Object prototype toString call  abc       object String  Object prototype toString call  abc       object RegExp  Object prototype toString call  1 2 3       object Array    One could write a short helper function such as  function type obj       return Object prototype toString call obj   match   s w    0  trim      return  object String  as String return  object Number  as Number return  object Object  as Object return  object Undefined  as Undefined return  object Function  as Function

User · Answer

You can use the instanceof operator to see if an object is an instance of another  but since there are no classes  you can t get a class name

User · Answer

Using Object prototype toString  It turns out  as this post details  you can use Object prototype toString - the low level and generic implementation of toString - to get the type for all built-in types  Object prototype toString call  abc       object String  Object prototype toString call  abc       object RegExp  Object prototype toString call  1 2 3       object Array    One could write a short helper function such as  function type obj       return Object prototype toString call obj   match   s w    0  trim      return  object String  as String return  object Number  as Number return  object Object  as Object return  object Undefined  as Undefined return  object Function  as Function

User · Answer

You can use the instanceof operator to see if an object is an instance of another  but since there are no classes  you can t get a class name

User · Answer

Say you have var obj   If you just want the name of obj s type  like  Object    Array   or  String   you can use this   Object prototype toString call obj  split      1  replace

User · Answer

I was actually looking for a similar thing and came across this question  Here is how I get types  jsfiddle  var TypeOf   function   thing          var typeOfThing   typeof thing       if    object      typeOfThing              typeOfThing   Object prototype toString call  thing             if     object Object       typeOfThing                  if   thing constructor name                     return thing constructor name                              else if           thing constructor toString   charAt 0                      typeOfThing   typeOfThing substring  8 typeOfThing length - 1                                else                    typeOfThing   thing constructor toString   match   function s   w                        if   typeOfThing                          return typeOfThing 1                                       else                       return  Function                                                       else               typeOfThing   typeOfThing substring  8 typeOfThing length - 1                         return typeOfThing charAt 0  toUpperCase     typeOfThing slice 1

User · Answer

Update To be precise  I think OP asked for a function that retrieves the constructor name for a particular object  In terms of Javascript  object does not have a type but is a type of and in itself  However  different objects can have different constructors  Object prototype getConstructorName   function         var str    this prototype   this prototype constructor   this constructor  toString       var cname   str match  function s  w     1      var aliases     quot  quot    quot anonymous quot    quot Anonymous quot       return aliases indexOf cname   gt  -1    quot Function quot    cname     new Array   getConstructorName        returns  quot Array quot   function          getConstructorName       returns  quot Function quot       Note  the below example is deprecated  A blog post linked by Christian Sciberras contains a good example on how to do it  Namely  by extending the Object prototype  if   Object prototype getClassName        Object prototype getClassName   function              return Object prototype toString call this  match     object s          1            var test    1 2 3 4 5    alert test getClassName        returns Array

User · Answer

A little trick I use   function Square        this className    Square       this corners   4     var MySquare   new Square    console log MySquare className       Square

User · Answer

Say you have var obj   If you just want the name of obj s type  like  Object    Array   or  String   you can use this   Object prototype toString call obj  split      1  replace

User · Answer

Fairly Simple    My favorite method to get type of anything in JS   function getType entity       var x   Object prototype toString call entity      return x split      1  split      0  toLowerCase        my favorite method to check type of anything in JS   function checkType entity  type       return getType entity      type

User · Answer

Update To be precise  I think OP asked for a function that retrieves the constructor name for a particular object  In terms of Javascript  object does not have a type but is a type of and in itself  However  different objects can have different constructors  Object prototype getConstructorName   function         var str    this prototype   this prototype constructor   this constructor  toString       var cname   str match  function s  w     1      var aliases     quot  quot    quot anonymous quot    quot Anonymous quot       return aliases indexOf cname   gt  -1    quot Function quot    cname     new Array   getConstructorName        returns  quot Array quot   function          getConstructorName       returns  quot Function quot       Note  the below example is deprecated  A blog post linked by Christian Sciberras contains a good example on how to do it  Namely  by extending the Object prototype  if   Object prototype getClassName        Object prototype getClassName   function              return Object prototype toString call this  match     object s          1            var test    1 2 3 4 5    alert test getClassName        returns Array

User · Answer

For of those of you reading this and want a simple solution that works fairly well and has been tested  const getTypeName    thing    gt      const name   typeof thing   if  name      object   return name   if  thing instanceof Error  return  error    if   thing  return  null    return      toString call thing  match   s  a-zA-Z      1  toLowerCase      To get insight on why this works  checkout the polyfill documentation for Array isArray    https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Array isArray polyfill

User · Answer

If anyone was looking for a solution which is working with jQuery  here is the adjusted wiki code  the original breaks jQuery    Object defineProperty Object prototype   getClassName         value  function             var funcNameRegex    function    1                var results    funcNameRegex  exec  this  constructor toString             return  results  amp  amp  results length  gt  1    results 1

User · Answer

You should use somevar constructor name like a    x000D   x000D       x000D      const getVariableType   a   gt  a constructor name toLowerCase    x000D   x000D      const d   new Date    x000D      const res1   getVariableType d       date  x000D      const num   5  x000D      const res2   getVariableType num       number  x000D      const fn        gt      x000D      const res3   getVariableType fn       function  x000D   x000D      console log res1       date  x000D      console log res2       number  x000D      console log res3       function  x000D   x000D   x000D

User · Answer

Is there a JavaScript equivalent of Java s class getName     No  ES2015 Update  the name of class Foo    is Foo name   The name of thing s class  regardless of thing s type  is thing constructor name  Builtin constructors in an ES2015 environment have the correct name property  for instance  2  constructor name is  quot Number quot    But here are various hacks that all fall down in one way or another  Here is a hack that will do what you need - be aware that it modifies the Object s prototype  something people frown upon  usually for good reason  Object prototype getName   function         var funcNameRegex    function    1           var results    funcNameRegex  exec  this  constructor toString        return  results  amp  amp  results length  gt  1    results 1     quot  quot       Now  all of your objects will have the function  getName    that will return the name of the constructor as a string  I have tested this in FF3 and IE7  I can t speak for other implementations  If you don t want to do that  here is a discussion on the various ways of determining types in JavaScript     I recently updated this to be a bit more exhaustive  though it is hardly that  Corrections welcome    Using the constructor property    Every object has a value for its constructor property  but depending on how that object was constructed as well as what you want to do with that value  it may or may not be useful  Generally speaking  you can use the constructor property to test the type of the object like so  var myArray    1 2 3    myArray constructor    Array      true  So  that works well enough for most needs  That said    Caveats Will not work AT ALL in many cases This pattern  though broken  is quite common  function Thingy       Thingy prototype         method1  function                method2  function               Objects constructed via new Thingy will have a constructor property that points to Object  not Thingy  So we fall right at the outset  you simply cannot trust constructor in a codebase that you don t control  Multiple Inheritance An example where it isn t as obvious is using multiple inheritance  function a     this foo   1   function b     this bar   2    b prototype   new a       b inherits from a  Things now don t work as you might expect them to  var f   new b       instantiate a new object with the b constructor  f constructor    b      false  f constructor    a      true  So  you might get unexpected results if the object your testing has a different object set as its prototype  There are ways around this outside the scope of this discussion  There are other uses for the constructor property  some of them interesting  others not so much  for now we will not delve into those uses since it isn t relevant to this discussion  Will not work cross-frame and cross-window Using  constructor for type checking will break when you want to check the type of objects coming from different window objects  say that of an iframe or a popup window  This is because there s a different version of each core type constructor in each  window   i e  iframe contentWindow Array     Array    false   Using the instanceof operator    The instanceof operator is a clean way of testing object type as well  but has its own potential issues  just like the constructor property  var myArray    1 2 3    myArray instanceof Array      true  myArray instanceof Object      true  But instanceof fails to work for literal values  because literals are not Objects  3 instanceof Number    false  abc  instanceof String    false true instanceof Boolean    false  The literals need to be wrapped in an Object in order for instanceof to work  for example new Number 3  instanceof Number    true  The  constructor check works fine for literals because the   method invocation implicitly wraps the literals in their respective object type 3  constructor     Number    true  abc  constructor     String    true true constructor     Boolean    true  Why two dots for the 3  Because Javascript interprets the first dot as a decimal point    Will not work cross-frame and cross-window instanceof also will not work across different windows  for the same reason as the constructor property check   Using the name property of the constructor property    Does not work AT ALL in many cases Again  see above  it s quite common for constructor to be utterly and completely wrong and useless  Does NOT work in  lt IE9 Using myObjectInstance constructor name will give you a string containing the name of the constructor function used  but is subject to the caveats about the constructor property that were mentioned earlier  For IE9 and above  you can monkey-patch in support  if  Function prototype name     undefined  amp  amp  Object defineProperty     undefined        Object defineProperty Function prototype   name             get  function                 var funcNameRegex    function s     s     s                  var results    funcNameRegex  exec  this  toString                 return  results  amp  amp  results length  gt  1    results 1     quot  quot                      set  function value                Updated version from the article in question  This was added 3 months after the article was published  this is the recommended version to use by the article s author Matthew Scharley  This change was inspired by comments pointing out potential pitfalls in the previous code  if  Function prototype name     undefined  amp  amp  Object defineProperty     undefined        Object defineProperty Function prototype   name             get  function                 var funcNameRegex    function s      1                    var results    funcNameRegex  exec  this  toString                 return  results  amp  amp  results length  gt  1    results 1  trim      quot  quot                      set  function value                 Using Object prototype toString It turns out  as this post details  you can use Object prototype toString - the low level and generic implementation of toString - to get the type for all built-in types Object prototype toString call  abc       object String  Object prototype toString call  abc       object RegExp  Object prototype toString call  1 2 3       object Array   One could write a short helper function such as function type obj       return Object prototype toString call obj  slice 8  -1      to remove the cruft and get at just the type name type  abc      String  However  it will return Object for all user-defined types   Caveats for all    All of these are subject to one potential problem  and that is the question of how the object in question was constructed  Here are various ways of building objects and the values that the different methods of type checking will return     using a named function  function Foo     this a   1    var obj   new Foo     obj instanceof Object               true  obj instanceof Foo                  true  obj constructor    Foo              true  obj constructor name     quot Foo quot        true     let s add some prototypical inheritance function Bar     this b   2    Foo prototype   new Bar    obj   new Foo     obj instanceof Object               true  obj instanceof Foo                  true  obj constructor    Foo              false  obj constructor name     quot Foo quot        false      using an anonymous function  obj   new  function     this a   1         obj instanceof Object                   true  obj constructor    obj constructor      true  obj constructor name     quot  quot               true      using an anonymous function assigned to a variable var Foo   function     this a   1     obj   new Foo     obj instanceof Object           true  obj instanceof Foo              true  obj constructor    Foo          true  obj constructor name     quot  quot       true      using object literal syntax obj     foo   1     obj instanceof Object                 true  obj constructor    Object             true  obj constructor name     quot Object quot       true  While not all permutations are present in this set of examples  hopefully there are enough to provide you with an idea about how messy things might get depending on your needs  Don t assume anything  if you don t understand exactly what you are after  you may end up with code breaking where you don t expect it to because of a lack of grokking the subtleties  NOTE  Discussion of the typeof operator may appear to be a glaring omission  but it really isn t useful in helping to identify whether an object is a given type  since it is very simplistic  Understanding where typeof is useful is important  but I don t currently feel that it is terribly relevant to this discussion  My mind is open to change though

User · Answer

If anyone was looking for a solution which is working with jQuery  here is the adjusted wiki code  the original breaks jQuery    Object defineProperty Object prototype   getClassName         value  function             var funcNameRegex    function    1                var results    funcNameRegex  exec  this  constructor toString             return  results  amp  amp  results length  gt  1    results 1

User · Answer

The kind   function from Agave JS will return    the closest prototype in the inheritance tree for always-primitive types like  null  and  undefined   the primitive name     It works on all JS objects and primitives  regardless of how they were created  and doesn t have any surprises  Examples   Numbers  kind 37       Number  kind 3 14       Number  kind Math LN2       Number  kind Infinity       Number  kind Number 1        Number  kind new Number 1        Number    NaN  kind NaN       NaN    Strings  kind          String  kind  bla        String  kind String  abc         String  kind new String  abc         String    Booleans  kind true       Boolean  kind false       Boolean  kind new Boolean true        Boolean    Arrays  kind  1  2  4        Array  kind new Array 1  2  3        Array    Objects  kind  a 1        Object  kind new Object         Object    Dates  kind new Date         Date    Functions  kind function           Function  kind new Function  console log arguments          Function  kind Math sin       Function    undefined  kind undefined       undefined    null  kind null       null

User · Answer

You should use somevar constructor name like a    x000D   x000D       x000D      const getVariableType   a   gt  a constructor name toLowerCase    x000D   x000D      const d   new Date    x000D      const res1   getVariableType d       date  x000D      const num   5  x000D      const res2   getVariableType num       number  x000D      const fn        gt      x000D      const res3   getVariableType fn       function  x000D   x000D      console log res1       date  x000D      console log res2       number  x000D      console log res3       function  x000D   x000D   x000D

User · Answer

For of those of you reading this and want a simple solution that works fairly well and has been tested  const getTypeName    thing    gt      const name   typeof thing   if  name      object   return name   if  thing instanceof Error  return  error    if   thing  return  null    return      toString call thing  match   s  a-zA-Z      1  toLowerCase      To get insight on why this works  checkout the polyfill documentation for Array isArray    https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Array isArray polyfill

[javascript] Get the name of an object's type

Examples related to javascript