Js面向对象之观察者模式

 //模拟一个目标可能拥有的一些列依赖
 function ObserverList() {
 this.observerList = [];
 };

 //添加一个观察者
 ObserverList.prototype.Add = function (obj) {
 return this.observerList.push(obj);
 };

 //清除所有观察者
 ObserverList.prototype.Empty = function () {
 this.observerList = [];
 };

 //获得所有观察者的数量
 ObserverList.prototype.Count = function () {
 return this.observerList.length;
 };

 //获取某个指定的观察者
 ObserverList.prototype.Get = function (index) {
 if (index > -1 && index < this.observerList.length) {
 return this.observerList[index];
 }
 };
 //插入一个观察者
 ObserverList.prototype.Insert = function (obj, index) {
 var pointer = -1;
 if (index === 0) {
 this.observerList.unshift(obj);
 pointer = index;
 } else if (index == this.observerList.length) {
 this.observerList.push(obj);
 pointer = index;
 }
 return pointer;
 };
 //从某个位置开始查找特定的观察者并返回观察者的索引值
 ObserverList.prototype.IndexOf = function (obj, startIndex) {
 var i = startIndex, pointer = -1;
 while (i < this.observerList.length) {
 if (this.observerList[i] == obj) {
 pointer = i;
 } i++;
 }
 return pointer;
 };

 //移除某个特定索引的观察者（如果存在）
 ObserverList.prototype.RemoveIndexAt = function (index) {
 if (index == 0) {
 this.observerList.shift();
 } else if (index == this.observerList.length - 1) {
 this.observerList.pop();
 }
 };

 //扩展对象
 function extend(obj, extension) {
 console.log(obj);
 for (var k in obj) {
 console.log(k);
 extension[k] = obj[k]
 }
 };

 //模拟一个目标对象，并模拟实现在观察者列表上添加、删除和通知观察者的能力
 function Subject() {
 this.observers = new ObserverList();
 };

 //目标添加一个观察者
 Subject.prototype.AddObserver = function (observer) {
 this.observers.Add(observer);
 };

 //目标对象移除某个观察者
 Subject.prototype.RemoveObserver = function (observer) {
 this.observers.RemoveIndexAt(this.observers.IndexOf(observer, 0));
 };

 Subject.prototype.RemoveAllObserver = function () {
 this.observers = [];
 }

 //模拟实现通知功能
 Subject.prototype.Notify = function (context) {
 var observerCount = this.observers.Count();
 for (var i = 0; i < observerCount; i++) {
 this.observers.Get(i).Update(context);
 }
 };
 //模拟创建一个观察者
 function Observer() {
 this.Update = function () {
 };
 }

 var controlCheckbox = document.getElementById("mainCheckBox");
 var removerObserver = document.getElementById("removerAllObserver");
 var addBtn = document.getElementById("addNewObserver");
 var container = document.getElementById("observerContainer");
 extend(new Subject(), controlCheckbox);

 controlCheckbox["onclick"] = Function("controlCheckbox.Notify(controlCheckbox.checked)");

 addBtn["onclick"] = AddNewObserver;
 function AddNewObserver() {
 var check = document.createElement("input");
 check.type = "checkbox";
 extend(new Observer(), check);
 check.Update = function (value) {
 this.checked = value;
 };
 controlCheckbox.AddObserver(check);
 container.appendChild(check);
 }