Sebastian Herrmann
A software-developing peep.
Building a browser extension in vanilla JavaScript
Insights and learnings
Hi! 👋
I’m Sebastian.
Frontend developer @
A quick history
Old workflow
Pocket + In My Pocket extension
New workflow
Omnivore + … ?
My extension
Omnivore List Popup!
My extension
Omnivore List Popup!
Features:
- Loads and displays Omnivore articles via their API
- Adding new articles
- Basic editing features (archiving, deleting, editing labels)
- Some handy links to the main Omnivore webapp
My extension
Available for Firefox and Chrome
“It’s going to be a simple little web app,
React seems like overkill here.”
Sebastian
Insights and
learnings
🌟 Good things
- In theory, web extensions are easy to build:
- HTML, CSS, JS, manifest.json
- Easy local development: Load the folder and use dev tools!
- The web extension standard is generally cool
- ✅ Chrome (incl. Chromium, Vivaldi, Brave, Arc, …)
- ✅ Firefox
- ✅ Safari (in theory)
🌟 Good things
- Great resources: MDN and Mozilla’s Extension Workshop
- Mozilla’s webextension-polyfill 👍
- Many open-source extensions to learn from
🌟 Good things
- It’s fun to reach out to the community, and see users and ratings coming in!
- … and they will ask for a Chrome port immediately.
💩 Bad things
Manifest V2 vs. Manifest V3 makes things complicated:
- V3 is contended and boycotted by many extensions.
- Firefox’s support isn’t complete yet (bug).
- I didn’t manage to migrate my API calls to V3 in Firefox.
- Some build tools help you maintain two sets of manifests, e.g. V2 for Firefox and V3 for Chrome.
💩 Bad things
Safari support isn’t worth it for me (Apple Developer Program → $99 per year).
💩 Bad things
People will make you shady offers …
💡 Learnings
Even a little extension like mine already has many UI states (to have a good UX):
- Onboarding state
- Loading state
- Error state (+ dedicated errors)
- Empty state
- Main state (list with pagination)
- Label modal
- Settings page
💡 Learnings
I quickly missed a lot of development features:
- Splitting code into multiple files
- Using TypeScript
- Auto-reload in the browser
💡 Learnings
I ended up building some Node scripts for:
- bundling files,
- processing manifests,
- preparing zip archives, …
… and eventually, I migrated to a less manual setup with Vite.
💡 Learnings
Next time I would use …
- A UI framework (Vue.js, React, Handlebars, …)?
- Third-party build tools:
- web-ext (commandline tool by Mozilla)
- Vite Plugin Web Extension
- A better test environment for the UI
💡 Bonus learning
CSS accent-color property for checkboxes 😍
Thank you!
Any questions?
Slides:
https://slides.com/herrherrmann/browser-extension
Source code:
https://github.com/herrherrmann/omnivore-list-popup/
Follow me:
@herrherrmann@mastodon.social
Building a browser extension in vanilla JavaScript
By Sebastian Herrmann
Building a browser extension in vanilla JavaScript
Insights and learnings from building the browser extension “Omnivore List Popup”.
