It's still a significant upgrade over JavaScript. I'm developing a web app with the Backend in Rust and Front-end in Vuejs/JavaScript. Sure Rust was slower to develop, but it doesn't throw errors like 'val in undefined' and then I have to go debugging where I check for the value of val. You do that beforehand on Rust and that avoid a whole class of problems.
JavaScript is cheaper to get started but becomes way more expensive to maintain. My Rust code on the other hand: Once it works it keeps working. If it compile it probably won't bug down the road.
I'd switch to Rust / WebAssembly once the libraries are mature/stable/documented enough. The overhead cost is worth it in the long run.
> JavaScript is cheaper to get started but becomes way more expensive to maintain.
I think this is assumption is a bit too broad. There is another side of this:
In JS you write less code than in Rust and there is less explicit coupling in a dynamic codebase. So changes tend to be smaller and faster as well.
For example if you pass a top-level data-structure X through A, B... and C but only C cares about some part Z. Then you change how Z is produced in A and consumed in C.
If you are dynamic you just do exactly that, which is actually just fine. In a static language you have to change all the B's. Or you take the time and write a sensible abstraction over Z or X so in the future you don't have to change the B's anymore, which is better, but ultimately less readable and more complex.
Stuff that is well understood and specified in advance suits a language like Rust better. You get all these runtime guarantees and performance. You get all this expressive (but explicit!) power to fine-tune abstractions and performance. It's great.
But the closer you get to a UI (especially GUI) and non-technical, direct(!) users, the more dynamic you want to be. Because in this context you are more of a human to computer translator: requirements get discovered via iterations, interactions need to be tested and evolve etc.
I've tried TypeScript and I didn't really like it. Plus you can ignore the strict type if you'd like to which is a slippery-slope if you are in a hurry to get something to market.
JavaScript is cheaper to get started but becomes way more expensive to maintain. My Rust code on the other hand: Once it works it keeps working. If it compile it probably won't bug down the road.
I'd switch to Rust / WebAssembly once the libraries are mature/stable/documented enough. The overhead cost is worth it in the long run.