Property or method "res" is not defined on the instance2019-12-14

Property or method "res" is not defined on the instance but referenced during render. Make sure that this property is reactive, either in the data option, or for class-based components, by initializing the property

百度的译文如下

属性或方法“res”未在实例上定义，但在呈现期间被引用。通过初始化该属性，确保该属性是被动的，无论是在数据选项中，还是对于基于类的组件

Vue中报这样的错误,让我找找了足足大半天,快要吐血了....其实就是使用某一个属性但是没有在,data中定义,故报错!

所以,必须在下面定义才好用!!!

data(){
    return {
        res:null
    }
}