A brief analysis of the two-way binding principle of complie data in Vue (detailed code explanation)

function node2Fragment(el) {
  var fragment = document.createDocumentFragment(),
    child;
  // 将原生节点拷贝到fragment
  while ((child = el.firstChild)) {
    fragment.appendChild(child);
  }

  return fragment;
}

//Compile
function Compile(el, vm) {
  this.$vm = vm;
  this.$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) {
    //...
  },

  //编译模板
  compileElement: function (el) {
    var childNodes = el.childNodes,
      self = this;
    [].slice.call(childNodes).forEach(function (node) {
      var text = node.textContent;
      var reg = /{{(.*)}}/; //表达式文本
      //按元素节点方式编译
      if (self.isElementNode(node)) {
        self.compile(node);
      } else if (self.isTextNode(node) && reg.test(text)) {
        self.compileText(node, RegExp.$1);
      }
      //遍历编译子节点
      if (node.childNodes && node.childNodes.length) {
        self.compileElement(node);
      }
    });
  },

  isElementNode: function (node) {
    return node.nodeType == 1;
  },

  isTextNode: function (node) {
    return node.nodeType == 3;
  },

  compileText: function (node, exp) {
    var self = this;
    var initText = this.$vm[exp];
    this.updateText(node, initText);
    new Watcher(this.$vm, exp, function (value) {
      self.updateText(node, value);
    });
  },

  updateText: function (node, value) {
    node.textContent = typeof value == "undefined" ? "" : value;
  },
};

Compile.prototype = {

  ......
  isDirective: function(attr) {
    return attr.indexOf('v-') == 0;
  },

  isEventDirective: function(dir) {
    return dir.indexOf('on:') === 0;
  },

  //处理v-指令
  compile: function(node) {

    var nodeAttrs = node.attributes,
      self = this;
    [].slice.call(nodeAttrs).forEach(function(attr) {
      // 规定：指令以 v-xxx 命名
      // 如 <span v-text="content"></span> 中指令为 v-text
      var attrName = attr.name; // v-text
      if (self.isDirective(attrName)) {
        var exp = attr.value; // content
        var dir = attrName.substring(2); // text
        if (self.isEventDirective(dir)) {
          // 事件指令, 如 v-on:click
          self.compileEvent(node, self.$vm, exp, dir);
        } else {
          // 普通指令如:v-model, v-html, 当前只处理v-model
          self.compileModel(node, self.$vm, exp, dir);
        }
        //处理完毕要干掉 v-on:, v-model 等元素属性
        node.removeAttribute(attrName)
      }
    });

  },

  compileEvent: function(node, vm, exp, dir) {

    var eventType = dir.split(&#39;:&#39;)[1];
    var cb = vm.$options.methods && vm.$options.methods[exp];
    if (eventType && cb) {
      node.addEventListener(eventType, cb.bind(vm), false);
    }

  },

  compileModel: function(node, vm, exp, dir) {

    var self = this;
    var val = this.$vm[exp];
    this.updaterModel(node, val);
    new Watcher(this.$vm, exp, function(value) {
      self.updaterModel(node, value);
    });
    node.addEventListener(&#39;input&#39;, function(e) {
      var newValue = e.target.value;
      if (val === newValue) {
        return;
      }
      self.$vm[exp] = newValue;
      val = newValue;
    });

  },

  updaterModel: function(node, value, oldValue) {
    node.value = typeof value == &#39;undefined&#39; ? &#39;&#39; : value;
  },

}

function Vue(options) {
  .....
  observe(this.data, this);
  this.$compile = new Compile(options.el || document.body, this)
  return this;

}

<!--html-->
<div id="app">
  <h2 id="name">{{name}}</h2>
  <input v-model="name" />
  <h1 id="name">{{name}}</h1>
  <button v-on:click="test">click here!</button>
</div>
<script>
  new Vue({
    el: "#app",
    data: {
      name: "chuchur",
      age: 29,
    },
    methods: {
      test() {
        this.name = "My name is chuchur";
      },
    },
  });
</script>