How to get a JavaScript Object's Class?

I created a Javascript Obj, but how can I get back the Class of that Javascript Obj?

I want something that similar to Java .getClass() method.

From stackoverflow

• There's no exact counterpart to Java's #getClass() in JavaScript. Mostly that's due to JavaScript being a prototype-based language, as opposed to Java being a class-based one.

  Depending on what you need #getClass() for, there are several options in JavaScript:

  • typeof()
  • instanceof
  • func.prototype, proto.isPrototypeOf
  • obj.constructor

  A few examples:

  function Foo() {}
  var foo = new Foo()
  
  typeof(foo) // == "object"
  
  foo instanceof Foo // == true
  foo.constructor // == Foo
  
  Foo.prototype.isPrototypeOf(foo) // == true
  Foo.prototype.bar = function (x) {return x+x}
  foo.bar(21) // == 42
  

  Miles : That should probably be `func.prototype` (yes, functions are objects, but the `prototype` property is only relevant on function objects).

  earl : Yes, good point.

  Christoph : you might also want to mention `instanceof`/`isPrototypeOf()` and the non-standard `__proto__`

  Christoph : ES5 has aditionally `Object.getPrototypeOf()`

  clarkf : For me, foo.constructor yields something different (Chrome 8.0.552.0 dev on Mac OS X): `Function Foo() {}`

  earl : Yes, clarkf, that's `Foo` pretty-printed. The comments don't indicate the return values, but equalities that hold for the return values. So the comment means that `foo.constructor == Foo` holds, which will also be the case for you.

• Javascript is a class-less languages: there are no classes that defines the behaviour of a class statically as in Java. JavaScript uses prototypes instead of classes for defining object properties, including methods, and inheritance. It is possible to simulate many class-based features with prototypes in JavaScript.

  shambleh : I have often said that Javascript lacks class :)

• You can get a reference to the constructor function which created the object by using the constructor property:

  function MyObject(){
  }
  
  var obj = new MyObject();
  obj.constructor; // MyObject
  

  If you need to confirm the type of an object at runtime you can use the instanceof operator:

  obj instanceof MyObject // true
  

• In javascript, there are no classes but i think you whant the constructor name so obj.constructor.toString() will tell you what you need.

• This function returns either "undefined", "null", or the "class" in [object class] from Object.prototype.toString.call(someObject).

  function getClass(obj) {
    if (typeof obj === "undefined")
      return "undefined";
    if (obj === null)
      return "null";
    return Object.prototype.toString.call(obj)
      .match(/^\[object\s(.*)\]$/)[1];
  }
  
  getClass("")   === "String";
  getClass(true) === "Boolean";
  getClass(0)    === "Number";
  getClass([])   === "Array";
  getClass({})   === "Object";
  getClass(null) === "null";
  // etc...