Class.js (Simple inheritance setup)

Class.js

function construct() {
  if ( this && typeof this.init === 'function' ) {
    this.init.apply( this, arguments );
  }
}

function extend( obj ) {
  var proto = Object.create( this && this.prototype || {} ),
    type = typeof obj,
    key;

  obj = type === 'function' ? obj.prototype : type === 'object' ? obj : {};

  function Class() {
    return this.constructor.apply( this, arguments );
  }

  for ( key in obj ) {
    if ( obj.hasOwnProperty( key ) ) {
      proto[ key ] = obj[ key ];
    }
  }
  
  Class.prototype = proto;
  proto.constructor = proto.constructor || construct;
  Class.extend = extend;

  return Class;
 
}

module.exports = extend.call( Object, { constructor: construct } );

example.js

var Class = require('./Class');
var EventEmitter = require('events').EventEmitter;

// Base class, inherits from EventEmitter
var Base = Class.extend( EventEmitter );

// Model class, adds basic setter/getter methods on top of EventEmitter
var Model = Base.extend({
  // As long as we inherit the default Class constructor,
  // this init method will be called on instantiation and passed
  // whatever arguments were received by the constructor
  init: function( obj ) {
    var key;
    this._attributes = {};
    for ( key in obj ) {
      this.set( key, obj[ key ] );
    }
  },
  set: function( key, val ) {
    this._attributes[ key ] = val;
    this.emit( 'change', key, val );
  },
  get: function( key ) {
    return this._attributes[ key ];
  }
});


// User class, adds some user-specific methods and attributes on top of Model
var User = Model.extend({
  avatarBaseURL: 'http://static.somedomain.com/avatars/{{id}}.jpg',
  getFullName: function() {
    return this.get('firstName') + ' ' + this.get('lastName');
  },
  getAvatarURL: function() {
    return this.avatarBaseURL.replace( /\{\{id\}\}/, this.get('id') );
  }
});


// Create a User instance with some data
var user = new User({
  firstName: 'John',
  lastName: 'Doe',
  id: 123
});

// Just a little proof that events work
user.on( 'change', function( key, val ) {
  console.log( '%s: %s', key, val );
});

// Set a new name, fire an event
user.set( 'firstName', 'Jane' );