'Avoid adding reactive properties to a Vue instance or its root $data ' + 'at runtime - declare it upfront in the data option.' ) return val } // 6. 無observe實(shí)例,直接賦值,// 返回值是設(shè)置的值 if (!ob) { target[key] = val return val } // 7. 收集依賴 defineReactive(ob.value...