If you're using Adobe Animate you would want to use AS3 for Android and iOS apps, it wouldn't make sense to do it in Javascript and then play the game inside a web view, inside an AIR app. I have had to do that, and it's full of difficulties. For desktop apps you would also use AS3, in an AIR app. For desktop web you would want to use AS3 and require the Flash Plugin, which most browsers have built in (Chrome, IE, Edge), and ones that don't (Safari and Firefox mainly) can have the plugin installed, if it isn't already.
If you must have the game work in a browser on mobile, then you have no choice but to use Javascript. You have to give up on some graphical abilities, and also you wouldn't be able to reuse much of your AS3 object oriented code, so it would be a rewrite of the code of the game.
The least amount of work to make a game in AS3 and Javascript formats at the same time would be to program the game in a non-OOP way, with ActionScript in the timeline, and doing as much as you can using graphics, that don't use any of the special abilities you only get with AS3 documents. Then you ought to be able to go through each script and adjust it to work for Javascript.
A better approach would be to make the best game you can in AS3, for the mobile and desktop apps, and desktop web, and then reuse as many graphics as possible, but rewrite the code in Javascript, to make a dumbed down version of the game for mobile browsers.
It's the same team that keeps both ActionScript and Javascript improvements coming along, so they both should have the same amount of future support.