LM Tech's blog

Software Architecture & Design Patterns

Despite being javascript an object oriented language, it doesn't use classes. Infact JavaScript is prototype based, not class based.
With javascript you can define and create your custom objects in many ways.

Direct Instance:

var o = new Object();
o.fName = "John";
o.lName = "Smith";
o.getFullName = function(){ return this.fName + " " + this.lName; };

The example above creates a new object's instance and adds two properties and one method. More...

The Liskov's Substitution Principle (LSP) was introduced by Barbara Jane Liskov in 1987.
It states that if class X is derived from a class Y, Y may be replaced with X without altering any of the desirable properties of the program.

Briefly: Subclasses should be substitutable for their base classes.

Ref.: http://en.wikipedia.org/wiki/Liskov_substitution_principle