js实现观察者模式

var publisher = {subscribers: {any: [] // event type: subscribers},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, type);},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);}}}}};function makePublisher(o) {var i;for (i in publisher) {if (publisher.hasOwnProperty(i) && typeof publisher[i] === "function") {o[i] = publisher[i];}}o.subscribers = {any: []};}var paper = {daily: function () {this.publish("big news today");},monthly: function () {this.publish("interesting analysis", "monthly");}};makePublisher(paper);var joe = {drinkCoffee: function (paper) {console.log('Just read ' + paper);},sundayPreNap: function (monthly) {console.log('About to fall asleep reading this ' + monthly);}};paper.subscribe(joe.drinkCoffee);paper.subscribe(joe.sundayPreNap, 'monthly');paper.daily();paper.daily();paper.daily();paper.monthly();