/*
 模型用于封裝與應(yīng)用程序的業(yè)務(wù)邏輯相關(guān)的數(shù)據(jù)以及對數(shù)據(jù)處理的方法。模型有對數(shù)據(jù)直接訪問的權(quán)利。
 模型不依賴 "視圖" 和 "控制器", 也就是說 模型它不關(guān)心頁面如何顯示及如何被操作.
*/
function Mode(elems) {
  // 所有元素
  this._elems = elems;
 
  // 被選中元素的索引
  this._selectedIndex = -1;
 
  // 增加一項(xiàng)
  this.itemAdd = new Event(this);
 
  // 刪除一項(xiàng)
  this.itemRemoved = new Event(this);
 
  this.selectedIndexChanged = new Event(this);
}
 
Mode.prototype = {
 
  constructor: 'Mode',
 
  // 獲取所有的項(xiàng)
  getItems: function(){
    return [].concat(this._elems);
  },
  // 增加一項(xiàng)
  addItem: function(elem) {
    this._elems.push(elem);
    this.itemAdd.notify({elem:elem});
  },
  // 刪除一項(xiàng)
  removeItem: function(index) {
    var item = this._elems[index];
    this._elems.splice(index,1);
    this.itemRemoved.notify({elem:item});
 
    if(index === this._selectedIndex) {
      this.setSelectedIndex(-1);
    }
  },
  getSelectedIndex: function(){
    return this._selectedIndex;
  },
  setSelectedIndex: function(index){
    var previousIndex = this._selectedIndex;
    this._selectedIndex = index;
    this.selectedIndexChanged.notify({previous : previousIndex});
  }
};
/*
 下面是觀察者模式類,它又叫發(fā)布---訂閱模式;它定義了對象間的一種一對多的關(guān)系，
 讓多個觀察者對象同時(shí)監(jiān)聽某一個主題對象，當(dāng)一個對象發(fā)生改變時(shí)，所有依賴于它的對象都將得到通知。
*/
function Event(observer) {
  this._observer = observer;
  this._listeners = [];
}
Event.prototype = {
  constaructor: 'Event',
  attach : function(listeners) {
    this._listeners.push(listeners);
  },
  notify: function(objs){
    for(var i = 0,ilen = this._listeners.length; i ) {
      this._listeners[i](this._observer,objs);
    }
  }
};
 
/*
 * 視圖顯示模型數(shù)據(jù)，并觸發(fā)UI事件。
 */
function View(model,elements){
  this._model = model;
  this._elements = elements;
 
  this.listModified = new Event(this);
  this.addButtonClicked = new Event(this);
  this.delButtonClicked = new Event(this);
  var that = this;
 
  // 綁定模型監(jiān)聽器
  this._model.itemAdd.attach(function(){
    that.rebuildList();
  });
  this._model.itemRemoved.attach(function(){
    that.rebuildList();
  });
 
  // 將監(jiān)聽器綁定到HTML控件上
  this._elements.list.change(function(e){
    that.listModified.notify({index: e.target.selectedIndex});
  });
  // 添加按鈕綁定事件
  this._elements.addButton.click(function(e){
    that.addButtonClicked.notify();
  });
  // 刪除按鈕綁定事件
  this._elements.delButton.click(function(e){
    that.delButtonClicked.notify();
  });
}
View.prototype = {
  constructor: 'View',
  show: function(){
    this.rebuildList();
  },
  rebuildList: function(){
    var list = this._elements.list,
      items,
      key;
    list.html("");
    items = this._model.getItems();
    for(key in items) {
      if(items.hasOwnProperty(key)) {
        list.append('' +items[key]+ '');
      }
    }
    this._model.setSelectedIndex(-1);
  }
};
/*
 控制器響應(yīng)用戶操作，調(diào)用模型上的變化函數(shù)
 負(fù)責(zé)轉(zhuǎn)發(fā)請求，對請求進(jìn)行處理
*/
function Controller(model,view) {
  this._model = model;
  this._view = view;
  var that = this;
 
  this._view.listModified.attach(function(sender,args){
    that.updateSelected(args.index);
  });
  this._view.addButtonClicked.attach(function(){
    that.addItem();
  });
  this._view.delButtonClicked.attach(function(){
    that.delItem();
  });
}
Controller.prototype = {
  constructor: 'Controller',
 
  addItem: function(){
    var item = window.prompt('Add item:', '');
    if (item) {
      this._model.addItem(item);
    }
  },
 
  delItem: function(){
    var index = this._model.getSelectedIndex();
    if(index !== -1) {
      this._model.removeItem(index);
    }
  },
 
  updateSelected: function(index){
    this._model.setSelectedIndex(index);
  }
};

<select id="list" size="10" style="width: 10rem">select>br/>
<button id="plusBtn"> + button>
<button id="minusBtn"> - button>

$(function () {
  var model = new Mode(['PHP', 'JavaScript']),
   view = new View(model, {
    'list' : $('#list'), 
    'addButton' : $('#plusBtn'), 
    'delButton' : $('#minusBtn')
    }),
    controller = new Controller(model, view);    
    view.show();
});

// 添加按鈕綁定事件
this._elements.addButton.click(function(e){
  that.addButtonClicked.notify();
});

this._view.addButtonClicked.attach(function(){
  that.addItem();
});

addItem: function(){
  var item = window.prompt('Add item:', '');
  if (item) {
    this._model.addItem(item);
  }
}

// 增加一項(xiàng)
addItem: function(elem) {
  this._elems.push(elem);
  this.itemAdd.notify({elem:elem});
},

// 綁定模型監(jiān)聽器
this._model.itemAdd.attach(function(){
   that.rebuildList();
});