I'm fascinated by WebAssembly and love that it exists but if anyone tells you they need to use WebAssembly to make the UI snappy I'd advise you interrogate that assertion thoroughly.

I don't want to speak to this example too deeply because I don't know it (I see they're doing all sorts of stuff with audio so maybe they do need WebAssembly) but modern JavaScript VMs are very, very fast. 99% of webapps are absolutely fine using JavaScript.

The far more important part of making snappy UIs is the Web Worker aspect. To my mind it's one of the key reasons native apps feel so much better than web ones: it's trivial to move an operation off the main thread, do an expensive calculation and then trivial to bring it back to the main thread again. Unfortuately the API for doing so on the web is extremely clunky, passing messages back and forth between a page context and a worker context. I'd recommend anyone thinking about this stuff to take a look at Comlink:

it lets you wrap a lot of this complication up in simple promises, though you still have to think hard about what code lives inside a worker and what does not. In my ideal world all the code would live in the same place and we'd be freely exchanging stuff like you can in Swift. "Don't do it on the main thread" feels like a mantra taught to every new native developer as soon as it can be, the same discipline simply doesn't exist on the web. But neither do the required higher level language features/APIs.

> if anyone tells you they need to use WebAssembly to make the UI snappy I'd advise you interrogate that assertion thoroughly.

Get prepared to be blown away by Makepad [0]. I have no affiliation with them, but just watched their most recent conference presentation [1]. The slides were made with Makepad itself and included, embedded, a full-blown IDE, a synthesizer app, a Mandelbrot to zoom in endlessly, and more. All running at 120fps. The presentation is for the most part live-coding with this setup.

What they want to do is bring coders and designers closer together, and while some code is in Rust they developed a DSL for the GUI parts that is close to how Figma works. These GUI's can run anywhere.

And I couldn't help thinking "Why would people have complicated stacks to create Web 2.0 apps for the Google Web, when they have this?", in other words an opportunity to break out of the browser straitjacket.

Btw. WebAssembly/WebGL isn't the only way in which Makepad is available. And while running well in the browser for a time, there were issues to be solved here (addressed in the presentation). And tbh this isn't a real answer to your assertion. Greg Johnston, creator of Leptos, has made a video with performance comparisons [2].

Edit: Adding a link to the synthesizer app I just found [3].

[0] https://github.com/makepad/makepad

[1] https://www.youtube.com/watch?v=rC4FCS-oMpg

[2] https://www.youtube.com/watch?v=4KtotxNAwME

[3] https://makepad.nl/makepad/examples/ironfish/src/index.html