Caffeine is a livecoding environment for web browsers, Node.js, and WebAssembly. After adding it to a webpage, you can use it to make live persistent changes to that page and other pages running Caffeine, without reloading. site 
github
VIMEO 286872152 Caffeine talk 25 August 2018 by Craig Latta
This is a tour of the interactive slides for a talk about Caffeine, https://caffeine.js.org/.
You can interact with Caffeine from JavaScript in several ways: * as a headless Web Worker, with which you post and receive messages (you are responsible for all DOM manipulation). * as an IDE in a headful IFrame, with Caffeine able to manipulate the DOM directly. * on a headless Node server, with which you also exchange messages (over a WebSocket). * through a headful DevTools panel IDE, using the Chrome Debugging Protocol to manipulate every page your browser is running.
Next: Caffeine Canvas