Setup Emacs for JavaScript Development with LSP

Recently I've been toying with JavaScript so I wanted to see if I could get a good development environment working inside Emacs. The adoption of the Language Server Protocol LSP has streamlined a lot of this process in 2025. What used to require lots of custom elisp code (see js2-mode) can now be handled with generic Emacs packages and a good Language Sever.

Installing a JavaScript Language Server (LSP)

According to the internet the best JavaScript language server is the TypeScript Language Server. This language server can also be used for vanilla JavaScript development as well.

Installing via NPM

Currently the TypeScript Language Server is not packaged in Debian so you have to install it via the node package manager NPM. I am not that familiar with NPM, but online instructions told me I should use sudo npm install -g to install it globally with root. I think this is a bad security practice, so I am just going to install it locally in my home directory where it can do less damage.

This article by James Pic provides a workaround that advises NPM to install programs in your home directory instead. All you have to do is add the following variables to your ~/.bashrc

export PATH=$HOME/.local/bin:$PATH
export NODE_PATH=$HOME/.local/lib/node_modules:$NODE_PATH
export npm_config_prefix=$HOME/.local

Apply those settings to your running shell with:

source ~/.bashrc

Now we can install the Typescript Language Server with:

npm install -g typescript-language-server typescript

You may need to log out and back in for Emacs to recognize the executable typescript-language-server is available in your path under ~/.local/bin.

Emacs Setup

Open a JavaScript file, run M-x eglot, and it should work out of the box. For some additional tweaks below is a minimal Emacs config. Checkout my complete init file to see my actual settings.

;; Emacs LSP Client (built into Emacs 29.1)
(use-package eglot
  :ensure t)

;; Optional, can run M-x eglot to start LSP manually
(use-package js-mode
  :hook ((js-mode . subword-mode)
         (js-mode . electric-pair-mode)
         (js-mode . eglot-ensure)
         (js-mode . completion-preview-mode)))

;; Drop-down completions
(use-package corfu
  :ensure t
  :hook ((prog-mode . corfu-mode)))

;; Add bindings for navigating to next/previous error
(use-package flymake
  :bind (:map prog-mode-map
              ("M-n" . flymake-goto-next-error)
              ("M-p" . flymake-goto-prev-error)))

Corfu is an optional package that will make completions appear as a drop-down menu, similar to a programming integrated development environment IDE. Start typing something then type 'M-TAB' to trigger the completion drop-down. This can be triggered automatically but I find that distracting.

Things I Still Need to Figure Out

This setup has given me the basic editing environment I wanted with drop-down completions, error checking, and documentation at point. Although there are still some additional enhancements I am hoping to add.

TODO Search for Documentation

Eldoc will show documentation for a function/variable when it is written in full which is helpful. The issue is I often don't know exactly what I am looking for. Ideally I need a way to search for potential matches and review all their reference info. The documentation is in the server so I just need a way to get it out…

TODO Live Editing A Web Page

Right now I am editing scripts and refreshing the browser manually to test. I need to streamline that process. I see there is an interesting firefox-javascript-repl package.

Conclusion

So far things are basically working as expected. I am actually really enjoying learning JavaScript. The post ES6 language spec is pretty fun to work with. I highly recommend javascript.info to get up to speed quickly on modern JavaScript.

Expect to see more posts about web development. I am looking forward to adding some interactivity to my website and working on some other web-based projects. Don't worry though, my website will always work great without JavaScript. It has to look good in eww after all.