I can assure you that doing it in TS would not have been any slower and you would have gained all the benefits that static type checking brings with it.
VueJS 3 in particular is much better suited to use TS than its predecessor (without any additional plugins).
Can probably add types later, and consider it once we get the project underway. I am not saying you are wrong, but I have heard TypeScript developers complain about the turnaround in development being slower.
In my experience, most people who complain about TS slowing down development are devs who've been working with pure JS for a while and haven't gotten over the (relatively brief) learning curve to adopt TS.
Migrations, however, are always painful:
1) You're going to end up writing code that ends up being difficult to type later; to the extent that you and every single other developer on the team is disciplined enough to avoid that, you may as well adopt the typing ahead of time
2) The support & tooling for managing "halfway" migrated JS -> TS projects "exists", but is obviously inferior to just "buying in" all the way
If you haven't put in a huge amount of work yet, I'd strongly suggest pivoting to Typescript ASAP. I don't know how Vue handles it but it performs beautifully for React.
Well, typescript being a superset of JavaScript, you can use TypeScript compiler and just write plain JavaScript.
The only difference is that you’ll be warned when you write inconsistent (buggy) code. And that your IDE will autocomplete with only compatible values.
There is absolutely no way typescript slows down development, you’re just totally free to ignore any or all of it. But it will help you more than you imagine.
tbf, the only valid reason not to use ts today is if your code targets directly the browser without any build step and is referenced as is by your html.
VueJS 3 in particular is much better suited to use TS than its predecessor (without any additional plugins).