OO.js is a simple javascript inheritance & mixin implementation. (Inspired by Json Resig's Simple JavaScript Inheritance & Base.js & a lot more)

Class is the root type.

Create a new type based on Class:

var Person = Class.extend({
    "init":function(name,age){
        this.name = name;
        this.age = age;
    },
    "echo":function(){
        return "name: "+this.name+", age: "+ this.age;
    },
    "someProp":"Person prop"
});

var p = new Person("lucy",23);
assert.equal("name: lucy, age: 23",p.echo(),"Person.echo");

Note: "init" is the constructor where all the initialiation is done.

Create a sub type again:

var Student = Person.extend(
    {
        "init":function(name,age, sno){
            this.superClass.init(name,age);
            this.sno = sno;         
        },
        "echo":function(msg){
            return this.superClass.echo()+", sno: "+ this.sno;
        },
        "learn":function(course){
            return "learn: "+course;
        },
        "someProp":"Student prop"
    }
);

var s = new Student("bob", 21, "1230");
assert.equal("name: bob, age: 21, sno: 1230", s.echo(),"call this.superClass.echo()");
assert.equal("learn: Math", s.learn("Math"),"extended new methods learn()" );

Note: use "this.superClass.method_name" to access super type functionality.

Do some mixins:

var Run = Class.extend({
    "run":function(meters){
        return "run "+meters +" meters";
    }
});

Student.mixin(Run);
 
assert.equal("run 123 meters", s.run(123) , "mixin Run."); // s is defined above

var Think = Class.extend({
    "think":function(){
        return "think";
    }
});

Student.mixin(Think,{
    "eat":function(){
        return "eat";
    }
});

assert.equal("think", s.think()," mixin Think"); 
assert.equal("eat", s.eat()," mixin eat");

Note: the mix sources (like "Run" here) can not have "init" function, and they should not depend on initialization in order to behave properly.