Chrome Extension Manifest V3 Libraries in Background

Question

I'm in the process of updating my chrome extension from manifest v2 to v3. Here's the old manifest:

Manifest V2:

{
"manifest_version": 2,
"name": "Legacy Search Assistant",
"version": "0.1.1",
"content_scripts": [
    {
        "matches": [
            "https://*.legacysite.io/*","*://*/api*"
        ],
        "js": ["jquery-3.6.0.min.js","content.js"]
    }
],
"options_page": "options.html",
"background": {
    "scripts": ["jsencrypt.min.js", "jquery-3.6.0.min.js", "background.js"]
},
"browser_action": {
    "default_icon":  "icon.png",
    "default_popup": "popup.html",
    "default_title": "Legacy Search"
},
"permissions": [
    "storage"
]
}

Since jsencrypt.min.js was already loaded in the manifest I was able to call it's functions in background.js, but now that I've gone to manifest v3 I am having problems getting the service worker to access this library.

For example, when I make this call in background.js:

importScripts("/scripts/jsencrypt.min.js");

It throws the following error:

Error handling response: Error: Failed to execute 'importScripts' on 'WorkerGlobalScope': The script at 'chrome-extension://<extension ID>/scripts/jsencrypt.min.js' failed to load.

If I click the link in the error it takes me directly to the library I want loaded.

I've already tried all of the fixes in this answer . Please help if you can.

Answer 1

importScripts() is old way to load scripts in workers.

Now we can use more modern, ES modules instead.

Starting from Chrome 91, we can use JavaScript modules in service workers.

Just set type property to module in the manifest.

{
"manifest_version": 3,
"background": {
  "service_worker": "background.js",
  "type": "module"
}

This loads the service worker as an ES module, which lets you use the import keyword in the service worker to import other modules. Ex-

// background.js
import * as module from './scripts/jsencrypt.min.js';

Answer 2

The solution I ended up using was to move all usage of jsencrypt to the content.js. This allowed the module to function correctly and will not expose the public key in the environment we use our chrome extension in.

After creation and initializing of the jsencrypt object I pass it to the background script via a message.