There are some people used it quite extensively for web development (both front and back-end). This year's Hong Kong Open Source Conference will feature two Haxe talks, both are web focused:

* https://hkoscon.org/2018/topic/haxe-better-javascript-practi...

* https://hkoscon.org/2018/topic/type-safe-rest-api-haxe

I believe there will be live streams, or you can checkout the video that will be available shortly after.

(I'm a member of the Haxe Foundation, also the organizer of the HKOSCon Haxe track)