I don't find it makes much difference. If I get any runtime errors, you can add breakpoints into your code and the compiled TypeScript looks very similar to the

I don't find it makes much difference. If I get any runtime errors, you can add breakpoints into your code and the compiled TypeScript looks very similar to the JavaScript most of the time, plus you can use sourcemaps. The test code you type into the console doesn't need to be written in TypeScript either. The build step going from editing in an IDE to the code running is only a couple of seconds maximum as well. Getting more errors to appear in your IDE at compile time compared to in the console speeds you up way more than any slowdown you'd get too e.g. being told a variable could be undefined at compile time is much faster to fix than having to wait for a runtime crash, you having to track down the cause then hoping you've fixed it.