regl with hot-server. Adapted from a rreusser demo.
Run with yarn && yarn run start. Edit script.js and the page will update without a full reload.
Dumping all the loaded libraries into global variables isn't particularly pretty. But it is way easier to see how your edits changed the page without the interrupting flash of white from reloading.
glslify could be better - not sure how to change the default function name.