I'm an artist and game designer (not a programmer) who has been creating HTML5 games for the past 7 years. The developers I've worked have primarily used Haxe and Flambe, as well as the occasional dabbling into Phaser. Speed Test Scrabble Word Finder Solitaire
For all these approaches, we've used Flump to create the majority of our animated assets (I don't think our Phaser runtime was ever shared with the community, however). It's proven to be an incredibly valuable tool, allowing us to create complex animations using Adobe Animate while keeping atlas sizes low. In the right hands, it's even allowed our artists to take on tasks that our developers might otherwise need to handle when animating flourishes on UI elements and other clever effects.