Scala

Looking forward - eventually - to trying out the wasm option, which might eventually help speed up my interactive climate-scenario model which already runs with scala.js. Although speed is not currently the limiting factor, a wasm option might expand the potential scope - for example to increase regional resolution. However I presume to do this I'd have to refactor the code a lot, to keep all the gui and io in js while pushing the intensive calculations to wasm, and create data interfaces between these (at a rather low level if i understand correctly?), which could get tricky as it’s tightly coupled, code evolved over 24 years ...
Puzzled why wasm is promoted for "backend", which already has other compilation targets (jvm, native), seems to me this is a bigger opportunity to do complex calculations in the browser.