The CreateJS suite covers most, if not all, of what Flash could do in JavaScript. In fact, it is the library used by Adobe Animate professional to export Flash programs to HTML5 target. It may not be as user-friendly, but it's as comprehensive.
OK, CreateJS with NanoFL, then. I prefer to work without GUI tools, but they are available if needed. But I readily grant that they are not advanced as the original Flash environment.
BTW, to those that downvoted this comment to -2, in HN we generally don't downvote to express disagreement.
The CreateJS suite covers most, if not all, of what Flash could do in JavaScript. In fact, it is the library used by Adobe Animate professional to export Flash programs to HTML5 target. It may not be as user-friendly, but it's as comprehensive.