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观察者

是一种管理人与任务之间的关系的得力工具，实质就是你可以对程序中某个对象的状态进行观察，并且在其发生改变时能够得到通知。一般有两种实现方式推或拉，在这个过程中各方的职责如下：

• 订阅者可以订阅和退订，他们还要接收，并且可以在由人投送和自己收取之间进行选择；
• 发布者负责投关，他们可以在送出和由人取之间进行选择；

function Publisher() {this.subscribers = [];
}
//投送方法
Publisher.prototype.deliver = function(data) {this.subscribers.forEach(function(fn) {fn(data);});return this;
};
//订阅方法
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;
};
//退订方法
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 dataconsole.log(data);// unsubscribe from this publisherarguments.callee.unsubscribe(publisherObject);
};
observerObject.subscribe(publisherObject);

动画

// Publisher API
var Animation = function(o) {this.onStart = new Publisher,//三个可监视时刻this.onComplete = new Publisher,this.onTween = new Publisher;
};
Animation.method('fly', function() {// begin animationthis.onStart.deliver();for ( ... ) { // loop through frames// deliver frame numberthis.onTween.deliver(i); }// end animationthis.onComplete.deliver();});// setup an account with the animation manager
var Superman = new Animation({...config properties...});// Begin implementing subscribers
var putOnCape = function(i) { };
var takeOffCape = function(i) { };putOnCape.subscribe(Superman.onStart);
takeOffCape.subscribe(Superman.onComplete);// fly can be called anywhere
Superman.fly();
// for instance:
addEvent(element, 'click', function() {Superman.fly();
});

事件监听器

var element = document.getElementById(‘a’);
var fn1 = function(e) {// handle click
};
var fn2 = function(e) {// do other stuff with click
};addEvent(element, ‘click’, fn1);
addEvent(element, ‘click’, fn2);

命令

是一种封装方法调用的方式，命令模式与普通函数不同。它可以用来对方法调用进行参数化处理和传送，经这样处理过的方法调用可以在任何需要的时候执行。它也可以用来消除调用操作的对象和实现操作的对象之间的耦合。

它在创建用户界面时非常有用，特别是在需要不受限制的取消操作的时候。它还可以用来替代回调函数 ，因为它能够提高在对象间传递的操作的模块化程度。

这种模式适合JSP中的ACTION的实现，在一个ACITON中封装多个命令，如果只封装一个就没有多大意思了。

/* AdCommand interface. */
var AdCommand = new Interface('AdCommand', ['execute']);/* StopAd command class. */
var StopAd = function(adObject) { // implements AdCommandthis.ad = adObject;
};
StopAd.prototype.execute = function() {this.ad.stop();
};/* StartAd command class. */
var StartAd = function(adObject) { // implements AdCommandthis.ad = adObject;
};
StartAd.prototype.execute = function() {this.ad.start();
};/* Useage. 这种方式后，就把按钮和他需要调用的操作之间解耦了*/
var startCommand = new StartAd(action);
var stopCommand = new StopAd(action);
new UiButton('Start ', startCommand);
new UiButton('Stop ', stopCommand);

/*匿名函数的写法，省略了很多代码*/
function makeStart(adObject) {return function() { adObject.start();};
}
function makeStop(adObject) {return function() {adObject.stop();};
}/* Implementation code. */
var startCommand = makeStart(ads[i]);
var stopCommand = makeStop(ads[i]);
startCommand(); 
stopCommand();

多数命令模式都由以下几种角色组成，客户创建命令，调用者执行命令，接收者在命令执行时执行相应的操作。

接口格式

var Command = new Interface('Command', ['execute']);
Interface.ensureImplements(someCommand, Command);
someCommand.execute();
if(typeof someCommand != 'function') {throw new Error('Command isn't a function');
}

命令对象格式

/* SimpleCommand, a loosely coupled, simple command class. */
var SimpleCommand = function(receiver) { // implements Commandthis.receiver = receiver;
};
SimpleCommand.prototype.execute = function() {this.receiver.action();
};/* ComplexCommand, a tightly coupled, complex command class. */
var ComplexCommand = function() { // implements Commandthis.logger = new Logger();this.xhrHandler = XhrManager.createXhrHandler();this.parameters = {};
};
ComplexCommand.prototype = {setParameter: function(key, value) {this.parameters[key] = value;},execute: function() {this.logger.log('Executing command');var postArray = [];for(var key in this.parameters) {postArray.push(key + '=' + this.parameters[key]);}var postString = postArray.join('&');this.xhrHandler.request('POST', 'script.php', function() {}, postString);}
};/* GreyAreaCommand, somewhere between simple and complex. */
var GreyAreaCommand = function(recevier) { // implements Commandthis.logger = new Logger();this.receiver = receiver;
};
GreyAreaCommand.prototype.execute = function() {this.logger.log('Executing command');this.receiver.prepareAction();this.receiver.action();
};var openCommand = new MenuCommand(fileActions.open);
var openMenuItem = new MenuItem('Open', openCommand);
fileMenu.add(openMenuItem);

取消操作

这种操作其实就是把堆栈和excute相反的操作结合使用。

var MoveUp = function(cursor) { // implements ReversibleCommandthis.cursor = cursor;
};
MoveUp.prototype = {execute: function() {cursor.move(0, -10);},undo: function() {cursor.move(0, 10);    }
};