Chrome Extension Svelte Boilerplate

A basic foundation boilerplate for rich Chrome Extensions using Svelte and Webpack to help you write modular and modern Javascript code, load CSS easily and automatic reload the browser on code changes.

Developing a new extension

I'll assume that you already read the Svelte docs, the Webpack docs and the Chrome Extension docs.

1. Check if your Node.js version is >= 6.
2. Clone the repository.
3. Install yarn.
4. Run yarn.
5. Change the package's name and description on package.json.
6. Change the name of your extension on src/manifest.json.
7. Run npm run start
8. Load your extension on Chrome following:
   1. Access chrome://extensions/
   2. Check Developer mode
   3. Click on Load unpacked extension
   4. Select the build folder.
9. Have fun.

Structure

All your extension's development code must be placed in src folder, including the extension manifest.

The boilerplate is already prepared to have a popup, a options page and a background page. You can easily customize this.

Each page has its own assets package defined. So, to code on popup you must start your code on src/js/popup.js, for example.

Svelte components are under src/svelte/*.svelte. The example popup component is provided at src/svelte/popup.svelte. .svelte extension is used to distiguish components from static html files, required for an extension.

Webpack auto-reload and HRM

To make your workflow much more efficient this boilerplate uses the webpack server to development (started with npm start) with auto reload feature that reloads the browser automatically every time that you save some file o your editor.

You can run the dev mode on other port if you want. Just specify the env var port like this:

$ PORT=6002 npm start

Content Scripts

Although this boilerplate uses the webpack dev server, it's also prepared to write all your bundles files on the disk at every code change, so you can point, on your extension manifest, to your bundles that you want to use as content scripts, but you need to exclude these entry points from hot reloading (why?). To do so you need to expose which entry points are content scripts on the webpack.config.js using the chromeExtensionBoilerplate -> notHotReload config. Look the example below.

Let's say that you want use the myContentScript entry point as content script, so on your webpack.config.js you will configure the entry point and exclude it from hot reloading, like this:

{
  …
  entry: {
    myContentScript: "./src/js/myContentScript.js"
  },
  chromeExtensionBoilerplate: {
    notHotReload: ["myContentScript"]
  }
  …
}

and on your src/manifest.json:

{
  "content_scripts": [
    {
      "matches": ["https://www.google.com/*"],
      "js": ["myContentScript.bundle.js"]
    }
  ]
}

Packing

After the development of your extension run the command

$ NODE_ENV=production npm run build

Now, the content of build folder will be the extension ready to be submitted to the Chrome Web Store. Just take a look at the official guide to more infos about publishing.

Secrets

If you are developing an extension that talks with some API you probably are using different keys for testing and production. Is a good practice you not commit your secret keys and expose to anyone that have access to the repository.

To this task this boilerplate import the file ./secrets.<THE-NODE_ENV>.js on your modules through the module named as secrets, so you can do things like this:

./secrets.development.js

export default { key: "123" };

./src/popup.js

import secrets from "secrets";
ApiCall({ key: secrets.key });

👉 The files with name secrets.*.js already are ignored on the repository.

Acknowledgement

I would like to thank Samuel Simões for Chrome Extension Webpack Boilerplate, which was used as a base for this project. Some of the readme instructions were also reused.