Hi Kaptan,
It is written in Typescript. And the advantage is having types, which help you prevent certain types of bugs, but more importantly, provide your fellow developers with information what you expect when you write a function.
example (simple on purpose!)

As you can see, when you use the function, you get an overview of all parameters, including the type. There will be a red underline if you are trying to give the wrong ammount of parameters, or wrong types. This alone speeds up development a lot.
Regards
Sander