Actually, JavaScript uses a different approach than C# or C++ to create an object-oriented language. It is a prototype-based language.

Such prototypal inheritance can effectively mimic class-based inheritance, without creating classes, in more than one way. See Dean Edwards’ base2, qooxdoo, Prototype for a few implementations.

With the exception of JavaScript, prototypal inheritance is not part of any mainstream language. To make matters worse, it’s possible to emulate the classical model in JavaScript.