浅谈使用MVC模式进行JavaScript程序开发

<select id="selAnimal">
  <option value="cat">cat</option>
  <option value="fish">fish</option>
  <option value="bird">bird</option>
</select>
<p id="whatDoesThisAnimalDo"></p>

<script type="text/javascript">
document.getElementById('selAnimal').onchange = function() {
  var thisAnimalDoes;
  switch ( this.value ) {
    case 'cat':
      thisAnimalDoes = "cat meows";
      break;
    case 'fish':
      thisAnimalDoes = "fish swims";
      break;
    case 'bird':
      thisAnimalDoes = "bird flies";
      break;
    default:
      thisAnimalDoes = "wuff?";
  }
  document.getElementById('whatDoesThisAnimalDo').innerHTML = thisAnimalDoes;
}
</script>

<select id="selAnimal">
  <option value="cat">cat</option>
  <option value="fish">fish</option>
  <option value="bird">bird</option>
</select>
<p id="whatDoesThisAnimalDo"></p>

<script type="text/javascript">
// whatDoesAnimalDo 就是一个controller
var whatDoesAnimalDo = {
  // 选择视图
  start: function() {
    this.view.start();
  },
  // 将用户的操作映射到模型的更新上
  set: function(animalName) {
    this.model.setAnimal(animalName);
  },
};
// whatDoesAnimalDo的数据model
whatDoesAnimalDo.model = {
  // animal的数据
  animalDictionary: {
    cat: "meows",
    fish: "swims",
    bird: "flies"
  },
  // 当前的animal，也就是这个application的状态
  currentAnimal: null,
  // 数据模型负责业务逻辑和数据存储
  setAnimal: function(animalName) {
    this.currentAnimal = this.animalDictionary[animalName] ? animalName : null;
    this.onchange();
  },
  // 并且通知视图更新显示
  onchange: function() {
    whatDoesAnimalDo.view.update();
  },
  // 还需要响应视图对当前状态的查询
  getAnimalAction: function() {
    return this.currentAnimal ? this.currentAnimal + " " + this.animalDictionary[this.currentAnimal] : "wuff?";
  }
};
// whatDoesAnimalDo的视图
whatDoesAnimalDo.view = {
  // 用户输入触发onchange事件
  start: function() {
    document.getElementById('selAnimal').onchange = this.onchange;
  },
  // 该事件将用户请求发送给控制器
  onchange: function() {
    whatDoesAnimalDo.set(document.getElementById('selAnimal').value);
  },
  // 视图更新显示的方法，其中视图会向model查询当前的状态，并将其显示给用户
  update: function() {
    document.getElementById('whatDoesThisAnimalDo').innerHTML = whatDoesAnimalDo.model.getAnimalAction();
  }
};
whatDoesAnimalDo.start();
</script>