There is. It's been around since WebGL was a thing.

http://www.pouet.net/prodlist.php?platform[]=JavaScript&page...

It is already there https://www.chromeexperiments.com/webgl , but it starts to be even more exciting if you think about effects which could be applied to web sites and HTML content... Bumb mapping, reflections, motion blur, elastic elements when dragging. Whole bunch of shaders https://www.shadertoy.com/browse

Demoscene is not about flashy graphics. It's about doing something beautiful with code (this includes the way the code uses the machine to do things that go beyond, like mode 13h).