If you want to target HTML5, then we support Haxe, JavaScript, TypeScript and (now) ActionScript 3.0 as input languages. This uses NPM for linking tools together.
If you want to target Flash or Adobe AIR targets (Android, iOS, Windows, macOS) then there already are Adobe-based workflows for using ActionScript 3.0.
It’s also worth mentioning you can use HTML5 + Electron to build desktop applications using all of the above languages.
Lastly, if you want to target HTML5, Flash, AIR, Android, iOS, Windows, macOS, Linux, WebAssembly, consoles and other targets using the OpenFL tools, Haxe is the only supported language today.