<div id="mvvm-app">
  <input type="text" v-model="word">
  <p>{{word}}</p>
  <button v-on:click="sayHi">change model</button>
</div>

<script src="./js/observer.js"></script>
<script src="./js/watcher.js"></script>
<script src="./js/compile.js"></script>
<script src="./js/mvvm.js"></script>
<script>
var vm = new MVVM({
  el: '#mvvm-app',
    data: {
      word: 'Hello World!'
    },
    methods: {
      sayHi: function() {
        this.word = 'Hi, everybody!';
      }
    }
  });
</script>

var data = {name: 'kindeng'};
observe(data);
data.name = 'dmq'; // 哈哈哈，監(jiān)聽(tīng)到值變化了 kindeng --> dmq

function observe(data) {
  if (!data || typeof data !== 'object') {
    return;
  }
  // 取出所有屬性遍歷
  Object.keys(data).forEach(function(key) {
   defineReactive(data, key, data[key]);
 });
};

function defineReactive(data, key, val) {
  observe(val); // 監(jiān)聽(tīng)子屬性
  Object.defineProperty(data, key, {
    enumerable: true, // 可枚舉
    configurable: false, // 不能再define
    get: function() {
      return val;
    },
    set: function(newVal) {
      console.log('哈哈哈，監(jiān)聽(tīng)到值變化了 ', val, ' --> ', newVal);
      val = newVal;
    }
  });
}

// ... 省略
function defineReactive(data, key, val) {
 var dep = new Dep();
  observe(val); // 監(jiān)聽(tīng)子屬性

  Object.defineProperty(data, key, {
    // ... 省略
    set: function(newVal) {
     if (val === newVal) return;
      console.log('哈哈哈，監(jiān)聽(tīng)到值變化了 ', val, ' --> ', newVal);
      val = newVal;
      dep.notify(); // 通知所有訂閱者
    }
  });
}

function Dep() {
  this.subs = [];
}
Dep.prototype = {
  addSub: function(sub) {
    this.subs.push(sub);
  },
  notify: function() {
    this.subs.forEach(function(sub) {
      sub.update();
    });
  }
};

// Observer.js
// ...省略
Object.defineProperty(data, key, {
 get: function() {
 // 由于需要在閉包內(nèi)添加watcher，所以通過(guò)Dep定義一個(gè)全局target屬性，暫存watcher, 添加完移除
 Dep.target && dep.addDep(Dep.target);
 return val;
 }
  // ... 省略
});

// Watcher.js
Watcher.prototype = {
 get: function(key) {
 Dep.target = this;
 this.value = data[key]; // 這里會(huì)觸發(fā)屬性的getter，從而添加訂閱者
 Dep.target = null;
 }
}

function Compile(el) {
  this.$el = this.isElementNode(el) ? el : document.querySelector(el);
  if (this.$el) {
    this.$fragment = this.node2Fragment(this.$el);
    this.init();
    this.$el.appendChild(this.$fragment);
  }
}
Compile.prototype = {
 init: function() { this.compileElement(this.$fragment); },
  node2Fragment: function(el) {
    var fragment = document.createDocumentFragment(), child;
    // 將原生節(jié)點(diǎn)拷貝到fragment
    while (child = el.firstChild) {
      fragment.appendChild(child);
    }
    return fragment;
  }
};

Compile.prototype = {
 // ... 省略
 compileElement: function(el) {
    var childNodes = el.childNodes, me = this;
    [].slice.call(childNodes).forEach(function(node) {
      var text = node.textContent;
      var reg = /\{\{(.*)\}\}/; // 表達(dá)式文本
      // 按元素節(jié)點(diǎn)方式編譯
      if (me.isElementNode(node)) {
        me.compile(node);
      } else if (me.isTextNode(node) && reg.test(text)) {
        me.compileText(node, RegExp.$1);
      }
      // 遍歷編譯子節(jié)點(diǎn)
      if (node.childNodes && node.childNodes.length) {
        me.compileElement(node);
      }
    });
  },

  compile: function(node) {
    var nodeAttrs = node.attributes, me = this;
    [].slice.call(nodeAttrs).forEach(function(attr) {
      // 規(guī)定：指令以 v-xxx 命名
      // 如 <span v-text="content"></span> 中指令為 v-text
      var attrName = attr.name; // v-text
      if (me.isDirective(attrName)) {
        var exp = attr.value; // content
        var dir = attrName.substring(2); // text
        if (me.isEventDirective(dir)) {
         // 事件指令, 如 v-on:click
          compileUtil.eventHandler(node, me.$vm, exp, dir);
        } else {
         // 普通指令
          compileUtil[dir] && compileUtil[dir](node, me.$vm, exp);
        }
      }
    });
  }
};

// 指令處理集合
var compileUtil = {
  text: function(node, vm, exp) {
    this.bind(node, vm, exp, 'text');
  },
  // ...省略
  bind: function(node, vm, exp, dir) {
    var updaterFn = updater[dir + 'Updater'];
    // 第一次初始化視圖
    updaterFn && updaterFn(node, vm[exp]);
    // 實(shí)例化訂閱者，此操作會(huì)在對(duì)應(yīng)的屬性消息訂閱器中添加了該訂閱者watcher
    new Watcher(vm, exp, function(value, oldValue) {
     // 一旦屬性值有變化，會(huì)收到通知執(zhí)行此更新函數(shù)，更新視圖
      updaterFn && updaterFn(node, value, oldValue);
    });
  }
};

// 更新函數(shù)
var updater = {
  textUpdater: function(node, value) {
    node.textContent = typeof value == 'undefined' ? '' : value;
  }
  // ...省略
};

function Watcher(vm, exp, cb) {
  this.cb = cb;
  this.vm = vm;
  this.exp = exp;
  // 此處為了觸發(fā)屬性的getter，從而在dep添加自己，結(jié)合Observer更易理解
  this.value = this.get(); 
}
Watcher.prototype = {
  update: function() {
    this.run(); // 屬性值變化收到通知
  },
  run: function() {
    var value = this.get(); // 取到最新值
    var oldVal = this.value;
    if (value !== oldVal) {
      this.value = value;
      this.cb.call(this.vm, value, oldVal); // 執(zhí)行Compile中綁定的回調(diào)，更新視圖
    }
  },
  get: function() {
    Dep.target = this; // 將當(dāng)前訂閱者指向自己
    var value = this.vm[exp]; // 觸發(fā)getter，添加自己到屬性訂閱器中
    Dep.target = null; // 添加完畢，重置
    return value;
  }
};
// 這里再次列出Observer和Dep，方便理解
Object.defineProperty(data, key, {
 get: function() {
 // 由于需要在閉包內(nèi)添加watcher，所以可以在Dep定義一個(gè)全局target屬性，暫存watcher, 添加完移除
 Dep.target && dep.addDep(Dep.target);
 return val;
 }
  // ... 省略
});
Dep.prototype = {
  notify: function() {
    this.subs.forEach(function(sub) {
      sub.update(); // 調(diào)用訂閱者的update方法，通知變化
    });
  }
};

function MVVM(options) {
  this.$options = options;
  var data = this._data = this.$options.data;
  observe(data, this);
  this.$compile = new Compile(options.el || document.body, this)
}

function MVVM(options) {
  this.$options = options;
  var data = this._data = this.$options.data, me = this;
  // 屬性代理，實(shí)現(xiàn) vm.xxx -> vm._data.xxx
  Object.keys(data).forEach(function(key) {
    me._proxy(key);
  });
  observe(data, this);
  this.$compile = new Compile(options.el || document.body, this)
}

MVVM.prototype = {
 _proxy: function(key) {
 var me = this;
    Object.defineProperty(me, key, {
      configurable: false,
      enumerable: true,
      get: function proxyGetter() {
        return me._data[key];
      },
      set: function proxySetter(newVal) {
        me._data[key] = newVal;
      }
    });
 }
};