SPA = single page application. You can make one entirely in Blazor and can host it on any static file host. Are you talking about Javascript specifically?
Last year I created a Blazor WASM app[1] to get familiar with the tech. It was a game based on the board-game from the 60's called "Acquire". Although it's using the WASM hosting model, I did use SignalR to facilitate the real-time game play between players. The "practice" mode against the crude AI is entirely WASM and can be "played" as a PWA completely offline.
I had intentions of finishing this out, but I got far enough that I learned what I needed to for now. I felt like it was pretty good considering it's probably less than 40 hours of work and I'm a mobile/desktop dev not a Web dev.
