JavaScript编程设计模式之观察者模式(Observer Pattern)实例详解

 function ObserverList(){ this.observerList = []; } ObserverList.prototype.Add = function( obj ){ return this.observerList.push( obj ); }; ObserverList.prototype.Empty = function(){ this.observerList = []; }; ObserverList.prototype.Count = function(){ return this.observerList.length; }; ObserverList.prototype.Get = function( index ){ if( index > -1 && index 

 function Subject(){ this.observers = new ObserverList(); } Subject.prototype.AddObserver = function( observer ){ this.observers.Add( observer ); }; Subject.prototype.RemoveObserver = function( observer ){ this.observers.RemoveAt( this.observers.IndexOf( observer, 0 ) ); }; Subject.prototype.Notify = function( context ){ var observerCount = this.observers.Count(); for(var i=0; i 

 // The Observer function Observer(){ this.Update = function(){ // ... }; } 

 // A very simple new mail handler // A count of the number of messages received var mailCounter = 0; // Initialize subscribers that will listen out for a topic // with the name "inbox/newMessage". // Render a preview of new messages var subscriber1 = subscribe( "inbox/newMessage", function( topic, data ) { // Log the topic for debugging purposes console.log( "A new message was received: ", topic ); // Use the data that was passed from our subject // to display a message preview to the user $( ".messageSender" ).html( data.sender ); $( ".messagePreview" ).html( data.body ); }); // Here's another subscriber using the same data to perform // a different task. // Update the counter displaying the number of new // messages received via the publisher var subscriber2 = subscribe( "inbox/newMessage", function( topic, data ) { $('.newMessageCounter').html( mailCounter++ ); }); publish( "inbox/newMessage", [{ sender:"hello@google.com", body: "Hey there! How are you doing today?" }]); // We could then at a later point unsubscribe our subscribers // from receiving any new topic notifications as follows: // unsubscribe( subscriber1, ); // unsubscribe( subscriber2 ); 

 // Publish // jQuery: $(obj).trigger("channel", [arg1, arg2, arg3]); $( el ).trigger( "/login", [{username:"test", userData:"test"}] ); // Dojo: dojo.publish("channel", [arg1, arg2, arg3] ); dojo.publish( "/login", [{username:"test", userData:"test"}] ); // YUI: el.publish("channel", [arg1, arg2, arg3]); el.publish( "/login", {username:"test", userData:"test"} ); // Subscribe // jQuery: $(obj).on( "channel", [data], fn ); $( el ).on( "/login", function( event ){...} ); // Dojo: dojo.subscribe( "channel", fn); var handle = dojo.subscribe( "/login", function(data){..} ); // YUI: el.on("channel", handler); el.on( "/login", function( data ){...} ); // Unsubscribe // jQuery: $(obj).off( "channel" ); $( el ).off( "/login" ); // Dojo: dojo.unsubscribe( handle ); dojo.unsubscribe( handle ); // YUI: el.detach("channel"); el.detach( "/login" ); 

 var pubsub = {}; (function(q) { var topics = {}, subUid = -1; // Publish or broadcast events of interest // with a specific topic name and arguments // such as the data to pass along q.publish = function( topic, args ) { if ( !topics[topic] ) { return false; } var subscribers = topics[topic], len = subscribers ? subscribers.length : 0; while (len--) { subscribers[len].func( topic, args ); } return this; }; // Subscribe to events of interest // with a specific topic name and a // callback function, to be executed // when the topic/event is observed q.subscribe = function( topic, func ) { if (!topics[topic]) { topics[topic] = []; } var token = ( ++subUid ).toString(); topics[topic].push({ token: token, func: func }); return token; }; // Unsubscribe from a specific // topic, based on a tokenized reference // to the subscription q.unsubscribe = function( token ) { for ( var m in topics ) { if ( topics[m] ) { for ( var i = 0, j = topics[m].length; i 

 // Another simple message handler // A simple message logger that logs any topics and data received through our // subscriber var messageLogger = function ( topics, data ) { console.log( "Logging: " + topics + ": " + data ); }; // Subscribers listen for topics they have subscribed to and // invoke a callback function (e.g messageLogger) once a new // notification is broadcast on that topic var subscription = pubsub.subscribe( "inbox/newMessage", messageLogger ); // Publishers are in charge of publishing topics or notifications of // interest to the application. e.g: pubsub.publish( "inbox/newMessage", "hello world!" ); // or pubsub.publish( "inbox/newMessage", ["test", "a", "b", "c"] ); // or pubsub.publish( "inbox/newMessage", { sender: "hello@google.com", body: "Hey again!" }); // We cab also unsubscribe if we no longer wish for our subscribers // to be notified // pubsub.unsubscribe( subscription ); // Once unsubscribed, this for example won't result in our // messageLogger being executed as the subscriber is // no longer listening pubsub.publish( "inbox/newMessage", "Hello! are you still there?" );