How to create a class using prototype.js

Creating PrototypeJS Classes is very similar to creating classes in normal OOP languages.

First start off by naming your class

var myClass = Class.create({ });

This will create an empty class - now populate it with methods, if you put a method initialize PrototypeJS will fire that as the constructor

var myClass = Class.create(
{
    initialize : function()
    {
        this.options = 0;
    }
});

You can setup anything you want in the initialize() method like default values or just initializing the properties of the class. Lets put in some other methods and show how to instantiate the class.

var myClass = Class.create(
{
    initialize : function()
    {
        this.options = 0;
    },

    testme : function()
    {
        this.options++;
    },

    showme : function()
    {
        alert(this.options);
        return this.options;
    }
});

var theClass = new myClass();

Lets take it one more step and call other methods within methods and pass options to the constructor.

var myClass = Class.create(
{
    initialize : function(option)
    {
        this.options = (option ? option : 0);

        this.testme();
    },

    testme : function()
    {
        this.options++;
    },

    showme : function()
    {
        alert(this.options);
        return this.options;
    }
});

var theClass = new myClass(200);
theClass.showme();

//will alert 201 and return 201

This is cool and all - but what about class inheritance? That is a big thing in OOP - lets say we have a separate class that is a child class of myClass. For any method that you are overriding in the child class you can pass a first variable as $super and that will refer to the parent's method of the same name - similar to a scope resolution

var myChildClass = Class.create(myClass,
{
    initialize : function($super,option)
    {
        $super(option);

        // the child class needs option's default value at 150 or whatever is 
        // passed so run the parent initialize first and then redefine the 
        // option property
        this.option = (option ? option : 150);

        // you can still run methods in the parent that are not overridden in 
        // the child
        this.testme();
    }
});

var child = new myChildClass();
child.showme();

//will alert() 151 and return 151

I hope this is helpful for you.

Here are some more complex real world examples from my github

https://github.com/jwestbrook/Prototype.Growler

https://github.com/jwestbrook/Prototype.Watermark

https://github.com/jwestbrook/bootstrap-prototype