Typescript style guide for interfaces

Question

this is a question that may not have a single correct answer, as I do realise coding styles are quite varied, especially between different languages, eg camel case function

Answer 1

I as prefix was big at some time for Java and C# (probably also others) but I don't think this is still considered a good idea but how can one change something that is used by the majority of developers and existing code base.

It's similar to hungarian notation which is universally considered bad practice. Just give it a meaningful name. If you have different kinds of Cars than make Car the universal interface and class FancyCar implements Car is much more natural. Things like prefixes just prevent people from thinking about what they really want to express. See also http://c2.com/cgi/wiki?IntentionRevealingNames

There are also languages like Dart (probably many others I don't know) where there is not such a clear distinction between interface and class. In Dart you can implement any class. The class' interface just acts as an interface.

update

I don't say naming is easy. In fact I think it's the most or at least among the most difficult parts of software development. It's just that the general consesus of "the elite" is that prefixes for technical reasons are not the best approach. This doesn't mean there are alternative that have only advantages and no drawbacks. It seems in this case naming like UserService, UserServiceImpl, MockUserService is used instead. This way in most parts of your code the most natural way UserService is used and the derivates only in prividers. Otherwise, as mentioned above, consistency is way more important. If some style is more common in the language you use, I suggest to use this in your code as well.