I publicly committed to the 100 Day of Code challenge today.
After geting a bit familiar with react, I used create-react-app to scaffold this simple game. It was interesting making it.
You can view it here: https://mikister.github.io/tic-tac-toe-react-100daysofcode/
And here's the code: https://github.com/mikister/tic-tac-toe-react-100daysofcode
Interestingly the most problematic part was adding the app to github pages. Here a github gist that helped me with this: