<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)聽子屬性

 Object.defineProperty(data, key, {
  // ... 省略
  set: function(newVal) {
   if (val === newVal) return;
   console.log('哈哈哈，監(jiān)聽到值變化了 ', 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Dep定義一個全局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
   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]);
  // 實例化訂閱者，此操作會在對應(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;
   }
  });
 }
};