Skewer
Live web development in Emacs
...Developers can send expressions or complete buffers from Emacs and evaluate them immediately on an attached page. JavaScript results appear in the minibuffer or a dedicated REPL, while CSS rules and HTML elements can be updated without reloading the document. Multiple browser windows or tabs may connect simultaneously and receive the same submitted code. The package includes an Emacs-hosted HTTP service, CORS support, and a userscript for attaching Skewer to arbitrary pages. It is written entirely in Emacs Lisp and is distributed through MELPA with its required dependencies. ...