I’m fairly certain that AppleScript will continue to exist on the Mac.
Whether that can be called „supported“ is another question.
In my opinion (!), it’s an outdated „language“ (in quotes because there’s not even a formal grammar for it, much like with Basic). It’s lacking nearly everything a contemporary language should offer:
- string methods
- regular expressions
- array methods
- introspection
- user-defined classes
- advanced data types like
Set
And it doesn’t exist anywhere but on the Mac. JavaScript, otoh, develops continually, is clearly defined and available everywhere. More benefits from learning that then AS – but that’s just me. OTOH, Apple’s JXA (JavaScript for Automation), the integration of JavaScript with Apple’s scripting technology, is unfinished and unpolished. It mostly works, but there are edge cases, especially with the ObjC bridge, where the results are surprising or code doesn’t work though it should.
And: every task can be solved in every programming language. It just might be easier in one than in the other.
As to „how do I start“: @pete31 has explained that several times, iirc. And there’s a ton of older texts on the Net dealing with that, eg at MacScripter. No need to repeat all that.