I'm happy to mentor work towards this bug. Please don't ask to be assigned to it, though you can say you're working on it - please respect other contributors comments as well. You'll be automatically assigned when you upload the first patches.

Here's what to do:

• Make sure you have a local build of Firefox up and running. Use these instructions if you haven't already.
  • If you need help setting up, ask in #introduction on Matrix
• Using the ESMification walkthrough as a guide:
  1. Run ./mach esmify --convert path/to/files
  2. Examine the output for any errors from ESLint and fix them.
  3. Next convert the imports - ./mach esmify --import . --prefix path/to/files
  4. Again, check for any errors and fix them.
  5. Run a build to check it passes.
  6. Also run ./mach eslint --fix path/to/files and check there are no raised failures
  7. Commit the changes with a commit messages such as "Bug nnnnnn - Convert path/to/files to ES modules. r?Standard8"
• Use moz-phab submit to submit the patches for review.

I am working on this

https://hg.mozilla.org/mozilla-central/rev/af3c4b83d415