JavaScript设计模式学习——Observer

function Publisher(){
    this.subscribers = [];
}

Publisher.prototype.deliver = function(data){
    this.subscribers.forEach(function(fn){
        fn(data);
    });
    return this;
}

Function.prototype.subscribe = function(publisher){
    var that = this;
    var alreadyExists = publisher.subscribers.some(function(el){
        if (el == that)
            return;
    });
    if (!alreadyExists) {
        publisher.subscribers.push(this);
    }
    return this;
}

Function.prototype.unsubscribe = function(publisher){
    var that = this;
    publisher.subscribers = publisher.subscribers.filter(function(el){
        if (el !== that) {
            return el;
        }
    });
    return this;
};

var publisherObject = new Publisher;
var observerObject = function(data) {
// process data
console.log(data);
// unsubscribe from this publisher
arguments.callee.unsubscribe(publisherObject);
};
observerObject.subscribe(publisherObject);