手寫vue雙向綁定數據

時間 2019-11-15

標籤手寫 vue 雙向綁定數據简体版

原文原文鏈接

來一張原理圖：html

實現思路：vue

　　（1）綁定data 種的數據，爲每一個數據添加指令。經過Object,defineProperty() 來通知屬性是否更改node

　　（2）找到每一個DOM節點的指令。綁定事件。並綁定watcherapp

　　（3）實現DOM事件改變以後，響應data數據，實現視圖更新測試

<!DocType>
<html>
  <title>vue 的雙向綁定事件</title>
  <body id="app">
    <input type="text" v-model="number"/>
    <span v-bind="number"></span>
    <input type="text" v-model="age"/>
    <span v-bind="age"></span>
  </body>
   
<script>
  function Vue (options) {
     this._init(options);
  }
  
  Vue.prototype._init = function (options) {
    this.$data = options.data;
    this.$methods = options.data.methods;
    this.$el = document.querySelector(options.el);
    this.$methods = options.methods;
    this.$key = '';
    
    this._binding = {};
    
    // 觀測數據
    this._observer(this.$data);
    
    this._complie(this.$el);
    
    // this._test(this.$data);
  }
  
  // 觀測數據
  Vue.prototype._observer = function (obj) {
    var value;
    let _this = this;
    for (key in obj) {
      if (obj.hasOwnProperty(key)) {
        this._binding[key] = {                                                                                                                                                          
          _directives: []
        };
        value = obj[key];
        if (typeof value === 'object') {
          this._observer(value);
        }
        Object.defineProperty(this.$data, key, {
          enumerable: true,
          configurable: true,
          get: function () {
            console.log(`獲取${value}`, key);
            return value;
          },
          set: function (newVal) {
            console.log('key:', key, _this.$key);
            if (value !== newVal) {
              value = newVal;
              _this._binding[_this.$key]._directives.forEach(function (item, index) {
                item.update();
              })
            }
          }
        })
      }
    }
  }
  
  // 爲DOM節點添加指令事件
  Vue.prototype._complie = function (root) {
    var _this = this;
    var nodes = root.children;
    for (var i = 0; i < nodes.length; i++) {
      var node = nodes[i];
      if (node.children.length) {
        this._complie(node);
      }

      if (node.hasAttribute('v-click')) {
        node.onclick = (function () {
          var attrVal = nodes[i].getAttribute('v-click');
          return _this.$methods[attrVal].bind(_this.$data);
        })();
      }

      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 Watcher(
            'input',
            node,
            _this,
            attrVal,
            'value'
          ))

          return function() {
            _this.$key = attrVal
            _this.$data[attrVal] =  nodes[key].value;
          }
        })(i));
      } 

      if (node.hasAttribute('v-bind')) {
        var attrVal = node.getAttribute('v-bind');
        _this._binding[attrVal]._directives.push(new Watcher(
          'text',
          node,
          _this,
          attrVal,
          'innerHTML'
        ))
      }
    }
  }
  
   function Watcher(name, el, vm, exp, attr) {
    this.name = name;         //指令名稱，例如文本節點，該值設爲"text"
    this.el = el;             //指令對應的DOM元素
    this.vm = vm;             //指令所屬myVue實例
    this.exp = exp;           //指令對應的值，本例如"number"
    this.attr = attr;         //綁定的屬性值，本例爲"innerHTML"

    this.update();
  }
  
  // 更新數據
  Watcher.prototype.update = function () {
    this.el[this.attr] = this.vm.$data[this.exp];
  }
  
  
  // 測試
  Vue.prototype._test = function($data) {
     var a = $data.number;
     $data.number = 32;
  }
  
  window.onload = function () {
    var app = new Vue({
      el: '#app',
      data: {
         number: 12,
         age: 444
      },
      methods: {}
    })
  }

</script>
</html>

相關標籤/搜索

每日一句

每一个你不满意的现在，都有一个你没有努力的曾经。