Yep, templates are type-checked, even though it's not JSX. Svelte is already running a compiler on the components anyway, to figure out the reactive stuff and to generate the minimal code required to update those specific spots in the HTML, so it can pass that code through TypeScript's checks. I'm almost certain they haven't reinvented their own TypeScript compiler here; I believe it's just passing off the type checking work to the existing TS checker.
One thing to mention or clarify maybe, is that Svelte's special syntax for {#if}'s and {#each}'s have real JS in the meat of them. Doing something like {#if a === 5}, the `a === 5` is parsed as actual JS. I really appreciated this after having used AngularJS (the 1.x versions) back in the day where it had its own half-baked flavor of JS for those embedded expressions and I was never sure if what I was writing would actually work.
I would say, if you've got a handful of minutes to spare, give the first few steps of the Svelte tutorial a try if you haven't (https://svelte.dev/tutorial). I think it does a good job of giving a feel for how it works.
It's written as a series of interactive examples where they teach a concept and you can try it in the editor on the page. I had a lot of aha moments when I initially went through it, having started off skeptical about the whole idea of going backwards to templates after React. There are just a lot of little things that worked "as they should", and moments that made me go "ohhh of course that just works, it's plain JS, I see."
One thing to mention or clarify maybe, is that Svelte's special syntax for {#if}'s and {#each}'s have real JS in the meat of them. Doing something like {#if a === 5}, the `a === 5` is parsed as actual JS. I really appreciated this after having used AngularJS (the 1.x versions) back in the day where it had its own half-baked flavor of JS for those embedded expressions and I was never sure if what I was writing would actually work.
I would say, if you've got a handful of minutes to spare, give the first few steps of the Svelte tutorial a try if you haven't (https://svelte.dev/tutorial). I think it does a good job of giving a feel for how it works.
It's written as a series of interactive examples where they teach a concept and you can try it in the editor on the page. I had a lot of aha moments when I initially went through it, having started off skeptical about the whole idea of going backwards to templates after React. There are just a lot of little things that worked "as they should", and moments that made me go "ohhh of course that just works, it's plain JS, I see."