Goes to show how much i don't want to use typescript flavored syntax.
fyi, i still like typescript and i still use it for IDE autocompletion, down-level compiling and generating d.ts. But I prefer buildless setup so much more cuz it's faster. and easier to copy paste it around into other projects and it's easier to debugging/fixing the original source if digging into node_modules folders then some minified obfusicated source
https://jimmywarting.github.io/you-might-not-need-typescript/