A Pen by Andrew Kirchmyer.

observer-pattern-(javascript-patterns).markdown

observer pattern (javascript patterns)

A Pen by Andrew Kirchmyer on CodePen.

License.

script.js

var publisher = {
    subscribers: {
        any: []
    },
    subscribe: function(fn, type) {
        type = type || 'any';
        if (typeof this.subscribers[type] === 'undefined') {
            this.subscribers[type] = [];
        }
        this.subscribers[type].push(fn);
    },
    unsubscribe: function(fn, type) {
        this.visitSubscribers('unsubscribe', fn, types);
    },
    publish: function(publication, type) {
        this.visitSubscribers('publish', publication, type);
    },
    visitSubscribers: function(action, arg, type) {
        var pubtype = type || 'any',
            subscribers = this.subscribers[pubtype],
            i,
            max = subscribers.length;
        
        for (i = 0; i < max; i += 1) {
            if (action === 'publish') {
                subscribers[i](arg);
            }
            else {
                if (subscribers[i] === arg) {
                    subscribers.splice(i, 1);
                }
            }
        } //for
    } //publisher.visitSubscribers
}; // publisher

function makePublisher(o) {
    var i;
    for (i in publisher) {
        if (publisher.hasOwnProperty(i) && typeof publisher[i] === 'function') {
             o[i] = publisher[i];   
        }
    }
    o.subscribers = {any: []};
}


// Create a new publisher
var paper = {
    daily: function() {
        this.publish('big news today');
    },
    monthly: function() {
        this.publish("interesting analysis", "monthly");
    }
}
makePublisher(paper);

// create a subscriber
var joe = {
    drinkCoffee: function(paper) {
        console.log('Just read ' + paper);
    },
    sundayPreNap: function(monthly) {
        console.log('About to fall asleep reading ' + monthly)
    }
};
paper.subscribe(joe.drinkCoffee);
paper.subscribe(joe.sundayPreNap, 'monthly');


// fire some events from the publisher
paper.daily();
paper.daily();
paper.daily();
paper.monthly();


// joe can become a publisher too
makePublisher(joe);
joe.tweet = function(msg) {
    this.publish(msg);
}

// and paper can be a subscriber of joe
paper.readTweets = function(tweet) {
    alert('call a big meeting! Someone ' + tweet);
};
joe.subscribe(paper.readTweets);

// fire an event from the new publisher, joe
joe.tweet('hated the paper today');