One thing I haven't seen mentioned yet in the replies is that often, people will already have type checking in their editor, with inline feedback. The iteration speed when it comes to fixing type errors is much faster that way, and then running type checking again to serve it up in the browser is unnecessarily slowing you down (and the type checker isn't really fast).
Another thing worth pointing out is that pretty much every editor that ha a TypeScript plugin uses TypeScript's language server to power it. The language server and the compiler are contained within the same binary (or at least they were) and use the same typechecking logic. So if you see an error in your IDE, you can be pretty confident that it'll be there when you build your code, and vice versa.
