vscode 'type aliases' can only be used in a .ts file.

使用react-native cli生成react-native项目，app.js中报该错误

'type aliases' can only be used in a .ts file.

解决方法:

在vscode扩展中搜索
@builtin TypeScript and JavaScript Language Features

禁用该扩展即可

参考:

https://stackoverflow.com/questions/48852007/type-aliases-can-only-be-used-in-a-ts-file
https://github.com/Microsoft/vscode-react-native/issues/631

2019/2/14补充解决方法

type Props = {};
export default class App extends Component<Props> {
  //...
}

删除type Props = {};这一行以及Component后面的
App组件的声明变成如下:

export default class App extends Component {
  //...
}