This guide will introduce you to some basic principles about inheritance in CocktailJS.

Creating a Class

It is very simple to create classes with CocktailJS. Let’s start with a very simple one. We want to create a Person class. The Person instance should be able to print a message in the console when we ask it to sayHi.

Person.js

var cocktail = require('cocktail'),
    Person = function(){};

cocktail.mix(Person, {

    sayHi: function(){
        console.log('Hi!');
    }
});

module.exports =  Person;

In the example above we just created a Person class with a method sayHi(). We can use our new class to instantiate some objects:

index.js

var Person = require('./Person'),
    joe;

joe = new Person();

joe.sayHi(); //will print "Hi!" in the console

Extending a Class

Once we have created our Person we may want to add more abstractions to our model. Let’s say we want to create a Pirate who is a Person and can sayHi() as well.

Pirate.js

var cocktail = require('cocktail'),
    Person   = require('./Person'),
    Pirate   = function(){};

cocktail.mix(Pirate, {
    '@extends': Person
});

module.exports = Pirate;

The example shows how to extend from Person class. In CocktailJS everything is perform as a mix. In this case we are telling the mix that we are extending from another class - Person - by passing the base class as a parameter in the @extends annotation. So, now Pirate is a Person and we can create some pirates objects:

index.js

var Person = require('./Person'),
    Pirate = require('./Pirate'),
    joe, jack;

joe = new Person();

joe.sayHi(); //will print "Hi!" in the console

jack = new Pirate();

jack.sayHi(); //will print "Hi!" in the console

Refactoring our classes

With the current abstraction we have no differences between Person and Pirate. Let’s introduce some changes about how each of them says “Hi”.

Person.js

var cocktail = require('cocktail'),
    Person = function(){};

cocktail.mix(Person, {
    
    greeting: 'Hello',

    sayHi: function(){
        console.log(this.greeting + "!");
    }
});

module.exports =  Person;

And now in Pirate we can override the greeting property with something more appropriate for a pirate:

Pirate.js

var cocktail = require('cocktail'),
    Person   = require('./Person'),
    Pirate   = function(){};

cocktail.mix(Pirate, {
    '@extends': Person,

    greeting: 'Ahoy'

});

module.exports = Pirate;

Done! If we execute now our index.js file we will have a console message like this:

$ node index.js
Hello!
Ahoy!