<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;
  }
 });
 }
};