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Is JavaScript object-oriented? (18)

Is JavaScript object-oriented?

Answer : Yes

It has objects which can contain data and methods that act upon that data. Objects can contain other objects.

  • It does not have classes, but it does have constructors which do what classes do, including acting as containers for class variables and methods.
  • It does not have class-oriented inheritance, but it does have prototype-oriented inheritance.

The two main ways of building up object systems are by inheritance (is-a) and by aggregation (has-a). JavaScript does both, but its dynamic nature allows it to excel at aggregation.

Some argue that JavaScript is not truly object oriented because it does not provide information hiding. That is, objects cannot have private variables and private methods: All members are public.

But it turns out that JavaScript objects can have private variables and private methods. (Click here now to find out how.) Of course, few understand this because JavaScript is the world's most misunderstood programming language.

Some argue that JavaScript is not truly object oriented because it does not provide inheritance. But it turns out that JavaScript supports not only classical inheritance, but other code reuse patterns as well.

Sources : http://javascript.crockford.com/javascript.html

There have been some questions about whether or not JavaScript is an object-oriented language. Even a statement, "just because a language has objects doesn't make it OO."

Is JavaScript an object-oriented language?


Everything in javascript is an object - classes are objects, functions are objects, numbers are objects, objects objects objects. It's not as strict about typing as other languages, but it's definitely possible to write OOP JS.


Hanselminutes episode 146 looks at OO Ajax. It was a good show and definitely a good show to help form an opinion.


I am responding this question bounced from another angle.

This is an eternal topic, and we could open a flame war in a lot of forums.

When people assert that JavaScript is an OO programming language because they can use OOD with this, then I ask: Why is not C an OO programming language? Repeat, you can use OOD with C and if you said that C is an OO programming language everybody will said you that you are crazy.

We could put here a lot of references about this topic in very old books and forums, because this topic is older than the Internet :)

JavaScript has not changed for many years, but new programmers want to show JavaScript is an OO programming language. Why? JavaScript is a powerful language, but is not an OO programming language.

An OO programming language must have objects, method, property, classes, encapsulation, aggregation, inheritance and polymorphism. You could implement all this points, but JavaScript has not them.

An very illustrate example: In chapter 6 of "Object-Oriented JavaScript" describe 10 manners to implement "inheritance". How many manners there are in Java? One, and in C++? One, and in Delphi (Object Pascal)? One, and in Objective-C? One.

Why is this different? Because Java, C++, Delphi and Objective-C are designed with OOP in mind, but not JavaScript.

When I was a student (in 1993), in university, there was a typical home work: Implement a program designed using a OOD (Object-oriented design) with a non-OO language. In those times, the language selected was C (not C++). The objective of this practices was to make clear the difference between OOD and OOP, and could differentiate between OOP and non-OOP languages.

Anyway, it is evidence that not all people have some opinion about this topic :)

Anyway, in my opinion, JavaScript is a powerful language and the future in the client side layer!


I think when you can follow the same or similar design patterns as a true OO language like Java/C#, you can pretty much call it an OO language. Some aspects are obviously different but you can still use very well established OO design pattersn.


I would say it has capabilities to seem OO. Especially if you take advantage of it's ability to create methods on an existing object (anonymous methods in some languages). Client script libraries like jquery (jquery.com) or prototype (prototypejs.org) are good examples of libraries taking advantage of this, making javascript behave pretty OO-like.


It is object oriented, but not based on classes, it's based on prototypes.


JavaScript is Object-Based, not Object-Oriented. The difference is that Object-Based languages don't support proper inheritance, whereas Object-Oriented ones do.

There is a way to achieve 'normal' inheritance in JavaScript (Reference here), but the basic model is based on prototyping.


JavaScript is a very good language to write object oriented web apps. It can support OOP because supports inheritance through prototyping also properties and methods. You can have polymorphism, encapsulation and many sub-classing paradigms.


JavaScript is object-oriented, but is not a class-based object-oriented language like Java, C++, C#, etc. Class-based OOP languages are a subset of the larger family of OOP languages which also include prototype-based languages like JavaScript and Self.


Javascript is not an object oriented language as typically considered, mainly due to lack of true inheritance, DUCK typing allows for a semi-true form of inheritance/polymorphism along with the Object.prototype allowing for complex function sharing. At its heart however the lack of inheritance leads to a weak polymorphism to take place since the DUCK typing will insist some object with the same attribute names are an instance of an Object which they were not intended to be used as. Thus adding attributes to random object transforms their type's base in a manner of speaking.


Languages do not need to behave exactly like Java to be object-oriented. Everything in Javascript is an object; compare to C++ or earlier Java, which are widely considered object-oriented to some degree but still based on primitives. Polymorphism is a non-issue in Javascript, as it doesn't much care about types at all. The only core OO feature not directly supported by the syntax is inheritance, but that can easily be implemented however the programmer wants using prototypes: here is one such example.


Objects in JavaScript inherit directly from objects. What can be more object oriented?


Technically it is a prototype language, but it's easy to to OO in it.


The short answer is Yes. For more information:

From Wikipedia:

JavaScript is heavily object-based. Objects are associative arrays, augmented with prototypes (see below). Object property names are associative array keys: obj.x = 10 and obj["x"] = 10 are equivalent, the dot notation being merely syntactic sugar. Properties and their values can be added, changed, or deleted at run-time. The properties of an object can also be enumerated via a for...in loop.

Also, see this series of articles about OOP with Javascript.


This is of course subjective and an academic question. Some people argue whether an OO language has to implement classes and inheritance, others write programs that change your life. ;-)

(But really, why should an OO language have to implement classes? I'd think objects were the key components. How you create and then use them is another matter.)



Yes, it is. However, it doesn't support all of the features one would expect in an object oriented programming language lacking inheritance and polymorphism. This doesn't mean, however, that you cannot simulate these capabilities through the prototyping system that is avaialble to the language.





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