报错：问题出现原因就是props 单向数据流问题
vue.esm.js?efeb:628 [Vue warn]: Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders. Instead, use a data or computed property based on the prop’s value. Prop being mutated: “myvalue”
使用中间变量
父组件
子组件
运行结果
