vue双向数据绑定知识点总结(4)

日期：2020-05-11 栏目：程序人生浏览：次

2.6 解析指令

怎么才能将view与model绑定；我们定义一个_xhcomplie函数来解析我们的指令（v-bind；v-model；v-clickde）并这这个过程中对view和model进行绑定

xhVue.prototype._xhcompile = function (root) {
 // root是id为app的element的元素；也就是根元素
 var _this = this;
 var nodes = root.children;
 for (var i = 0,len = nodes.length; i < len; i++) {
  var node = nodes[i];
  if (node.children.length) {
   // 所有元素进行处理
   this._xhcompile(node)
  };
  // 如果有v-click属性；我们监听他的click事件；触发increment事件，即number++
  if (node.hasAttribute('v-click')) {
   node.onclick = (function () {
    var attrVal = nodes[i].getAttribute('v-click');
    // bind让data的作用域与methods函数的作用域保持一致
    return _this.$method[attrVal].bind(_this.$data);
   })();
  };
  // 如果有v-model属性；并且元素是input或者textrea；我们监听他的input事件
  if (node.hasAttribute('v-model') && (node.tagName = 'INPUT' || node.tagName == 'TEXTAREA')) {
   node.addEventListener('input', (function (key) {
    var attrVal = node.getAttribute('v-model');
    _this._binding[attrVal]._directives.push(new xhWatcher(
     'input', 
     node, 
     _this,
     attrVal, 
     'value'
    ));
    return function () {
     // 让number的值和node的value保持一致；就实现了双向数据绑定
     _this.$data[attrVal] = nodes[key].value
    }
   })(i));
  };
  // 如果有v-bind属性；我们要让node的值实时更新为data中number的值
  if (node.hasAttribute('v-bind')) {
   var attrVal = node.getAttribute('v-bind');
   _this._binding[attrVal]._directives.push(new xhWatcher(
    'text', 
    node, 
    _this,
    attrVal,
    'innerHTML'
   ))
  }
 }
}

并且将解析函数也加到_init函数中

xhVue.prototype._init = function(options){
 this.$options = options;
 this.$el = document.querySelector(options.el);
 this.$data = options.data;
 this.$method = options.methods;
 
 this._binding = {}; // _binding
 this._xhob(this.$data);
 this._xhcompile(this.$el);
}

最后

<!DOCTYPE html>
<html lang="en">

<head>
 <meta charset="UTF-8">
 <title>Document</title>
</head>
<body>
 <div id="app">
  <form>
   <input type="text" v-model="number">
   <button type="button" v-click="increment">增加</button>
  </form>
  <h3 v-bind="number"></h3>
 </div>
</body>
<script>
 function xhVue(options) {
  this._init(options);
 }
 xhVue.prototype._init = function (options) {
  this.$options = options;
  this.$el = document.querySelector(options.el);
  this.$data = options.data;
  this.$method = options.methods;

  this._binding = {}; // _binding
  this._xhob(this.$data);
  this._xhcompile(this.$el);
 }

 xhVue.prototype._xhob = function (obj) {
  var value;
  for (key in obj) {
   if (obj.hasOwnProperty(key)) {
    this._binding[key] = {
     _directives: []
    }
    value = obj[key];
    if (typeof value === 'object') {
     this._xhob(value);
    }
    var binding = this._binding[key];
    Object.defineProperty(this.$data, key, {
     enumerable: true,
     configurable: true,
     get: function () {
      console.log(`get${value}`)
      return value;
     },
     set: function (newVal) {
      if (value !== newVal) {
       value = newVal;
       console.log(`set${newVal}`)
       // 当number改变时；触发_binding[number]._directives中已绑定的xhWatcher更新
       binding._directives.forEach(function (item) {
        item.update();
       });
      }
     }
    })
   }
  }
 }

 xhVue.prototype._xhcompile = function (root) {
  // root是id为app的element的元素；也就是根元素
  var _this = this;
  var nodes = root.children;
  for (var i = 0, len = nodes.length; i < len; i++) {
   var node = nodes[i];
   if (node.children.length) {
    // 所有元素进行处理
    this._xhcompile(node)
   };
   // 如果有v-click属性；我们监听他的click事件；触发increment事件，即number++
   if (node.hasAttribute('v-click')) {
    node.onclick = (function () {
     var attrVal = node.getAttribute('v-click');
     console.log(attrVal);
     // bind让data的作用域与method函数的作用域保持一致
     return _this.$method[attrVal].bind(_this.$data);
    })();
   };
   // 如果有v-model属性；并且元素是input或者textrea；我们监听他的input事件
   if (node.hasAttribute('v-model') && (node.tagName = 'INPUT' || node.tagName == 'TEXTAREA')) {
    node.addEventListener('input', (function (key) {
     var attrVal = node.getAttribute('v-model');
     _this._binding[attrVal]._directives.push(new xhWatcher(
      'input',
      node,
      _this,
      attrVal,
      'value'
     ));
     return function () {
      // 让number的值和node的value保持一致；就实现了双向数据绑定
      _this.$data[attrVal] = nodes[key].value
     }
    })(i));
   };
   // 如果有v-bind属性；我们要让node的值实时更新为data中number的值
   if (node.hasAttribute('v-bind')) {
    var attrVal = node.getAttribute('v-bind');
    _this._binding[attrVal]._directives.push(new xhWatcher(
     'text',
     node,
     _this,
     attrVal,
     'innerHTML'
    ))
   }
  }
 }

 function xhWatcher(name, el, vm, exp, attr) {
  this.name = name; // 指令名称；对于文本节点；例如text
  this.el = el; // 指令对应DOM元素
  this.vm = vm; // 指令所属vue实例
  this.exp = exp; // 指令对应的值；例如number
  this.attr = attr; // 绑定的属性值；例如innerHTML
  this.update();
 }
 xhWatcher.prototype.update = function () {
  this.el[this.attr] = this.vm.$data[this.exp];
  // 例如h3的innerHTML = this.data.number;当numner改变则会触发本update方法；保证对应的DOM实时更新
 }
 var app = new xhVue({
  el: '#app',
  data: {
   number: 0
  },
  methods: {
   increment: function () {
    this.number++;
   }
  }
 });
</script>

</html>

转载注明出处：http://www.heiqu.com/222.html

vue双向数据绑定知识点总结(4)

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