今天我做React开发时，遇到如下的错误消息：
> Error: Invalid hook call. Hooks can only be called inside of the body of a function component. This could happen for one of the following reasons:
1. You might have mismatching versions of React and the renderer (such as React DOM)
2. You might be breaking the Rules of Hooks
3. You might have more than one copy of React in the same app
See https://fb.me/react-invalid-hook-call for tips about how to debug and fix this problem.
这个错误输出已经提醒了我，出错误的代码在我的应用程序MyApp.jsx里：
原来是我这段const变量初始化代码写到function外部了：
将其移至内部后错误消失：