We build a full game creation IDE and game engine which is entirely browser-based and almost entirely written in JavaScript (including all the performance-sensitive stuff), and the performance is ridiculously good[1]. You don't need WASM for good performance[2].
Fair enough, Construct looks cool. If you or anyone from your team is interested in doing an interview for a technical newsletter about browser-based apps[1] I'd be glad to get a JS perspective on high performance in the browser.
[1] https://www.construct.net/en/blogs/construct-official-blog-1...
[2] https://surma.dev/things/js-to-asc/