Errors getting started

[MincePie]

I'm really confused as to how this works in codepen but does not actually work.

I have tried to get help to work thorugh this tutorial (https://stackoverflow.com/questions/47025240/react-syntax-how-to-write-in-es6) and it seems syntax errors are acknowledged -but then it doesn't make sense to me that the code could be incorrect and still work in code pen:

[rebeccazeng]

I'm not sure if this is the case, but the npm modules or something in regard to React might be outdated.