Well — it was React: https://html5experts.jp/shumpei-shiraishi/24538/

(warning: translation autogenerated by Google)

(thanks @colingourlay and @jaames!)

Nintendo eShop is built with React! Shiraishi: In this session, we'll be looking at Nintendo eShop. Tsuda: Yes, Nintendo eShop is the Nintendo Switch shop. It also provides a service that allows you to purchase game software from your smartphone even when you don't have a Switch. Both are created on the web. Shiraishi: That kind of multi-platform development is what the Web excels at. Horikawa: That's right. The parts that can be seen on smartphones and PCs are made responsive, and a large part of the code can be shared. However, when operating on a game console, the controls are operated with buttons, so the code is slightly different. The eShop is fairly large-scale for a web app, but the architecture is unified across the board, using React as the foundation of the architecture . Shiraishi: Oh, you're using React! As a web engineer, it makes my heart pound to see React running inside the Nintendo Switch. What was the process for creating the eShop? Horikawa: The project started at the end of 2015. The Switch was released in March 2017, so the project started a little over a year before that. The keyword we relied on when creating the eShop was"immediately."