One of the better known contenders in the field of 2D game engines for the browser. Very code heavy but you'll definitely feel at home, if this is your jam. It just released a complete rewrite with version 3.
Another 2D engine and the one I started game development with. It's a bit smaller and with it's entity component system more opinionated than Phaser, but I think it's a solid foundation too. It released it a new version this month too.
A lesser known contender, also 2D, that helps you to create games with React. It offers basic concepts like a game loop or stages. It also works with React-Native, which makes native mobile games possible. Probably not suited for bigger projects, but certainly a simple way for React devs to get something running quickly.
This time a 3D engine that works with the power of WebGL, WebVR and WebAudio. If you're not the 2D type, but also want to keep things inside the browser. As the other engines I mentioned here, it's more coding heavy than major engines, but if you aren't into big things like the Unreal Engine (C++) or Unity (C#), Babylon is the way to go.