From Mozilla: An overview of the object-oriented capabilities of JavaScript. This covers OO concepts of classes and objects, instances, abstraction, encapsulation and polymorphism as done in JavaScript with functions and prototypal inheritance.
Although JavaScript is a class-free, object-oriented language using prototypal inheritance, it can still be used in a classical object-oriented way. Douglas Crockford compares the two inheritance-based systems, adding syntactic sugar to JavaScript to allow classical inheritance, and demonstrates a number of patterns that are not available in classical languages.
An elegant mechanism for extending and overriding JavaScript classes in an object oriented fashion. It eases the pain of object oriented JavaScript.