Observable - Pub/Sub

inherit.js

/**
 * Class inheritance helper
 * @param {function} Class - sub class
 * @param {function} Super - super class
 */
function extend(Class, Super) {
    if (typeof Class !== 'function' && typeof Super !== 'function') {
        return;
    }
    
    Class.prototype = Object.create(Super.prototype);
    Class.prototype.constructor = Class;
};

Observable.js

/**
 * Provides basic Pub/Sub interface and functionality
 *
 * @class Observable
 */
function Observable() {
    this.subscribers = [];
}

/**
 * Publishes the provided arguments to the subscribers.
 */
Observable.prototype.publish = function () {
    var args = Array.prototype.slice.call(arguments);
    
    this.subscribers.forEach(function (subscriber) {
        subscriber.onChange.apply(subscriber, args);
    });
};

/**
 * Ensures that the subscriber will be notified when publishing.
 * @param    {object}   subscriber
 * @property {function} subscriber.onChange - callback to be executed when publishing
 */
Observable.prototype.subscribe = function (subscriber) {
    var index = this.subscribers.indexOf(subscriber);
    if (index === -1 && typeof subscriber.onChange === 'function') {
        this.subscribers.push(subscriber);
    }
};

Observable.prototype.unsubscribe = function (subscriber) {
    var index = this.subscribers.indexOf(subscriber);
    if (index > -1) {
        this.subscribers.splice(index, 1);
    }
};

Property.js

/**
 * Stores a value and provides Pub/Sub features for value changes.
 *
 * @class    Property
 * @extends {Observable}
 * 
 * @param {*} value - initial value
 */
function Property(value) {
    Observable.apply(this, arguments);
    this.value = value;
}

extend(Property, Observable);

Property.prototype.get = function () {
    return this.value;
};

Property.prototype.set = function (value) {
    this.value = value;
    this.publish(this);
};

Subscriber.js

/**
 * Base Subscriber class to provide a noop Subscriber#onChange method
 */
function Subscriber() {}

Subscriber.prototype.onChange = function () {};