vue-源码

添加__ob__属性，值为Observer

    function def (obj, key, val, enumerable) {      //obj 为观察数据对象，eg :{a:1}      //key 为 __ob__      //val 为 Observer{          dep: Dep{id: 2subs: []},          value: {a: 1},          vmCount: 0,      }            Object.defineProperty(obj, key, {        value: val,        enumerable: !!enumerable,        writable: true,        configurable: true      });    }            /**     * Walk through all properties and convert them into     * getter/setters. This method should only be called when     * value type is Object.     */    Observer.prototype.walk = function walk (obj) {      var keys = Object.keys(obj);      for (var i = 0; i < keys.length; i++) {        defineReactive$$1(obj, keys[i]);      }    };        //判断是不是obj     function isObject (obj) {      return obj !== null && typeof obj === 'object'    }