I think they use something called “flow” last time I’ve checked, it’s like typescript but when I went to visit the website with more information it was so slow it crashed my browser.
You may be right. I think Flow was a predecessor to TypeScript.
I just checked out Flow and woah. First-class syntax sugar for React. Maybe cool. (If it doesn't break catastrophically in a sane build system like Vite)
Are you sure? The React compiler is a fairly new addition to React, Flow is Facebook's old alternative to Typescript, but Typescript won the ecosystem in terms of broad adoption in the end. I think Flow is barely used today, I would be really surprised if they choose it for a new tool, even for a Facebook project.
You may be thinking about React itself, not the new compiler? I'm sure there must be some flow in there still from back in the day.