A brilliant add-on, simple to setup and use, and did exactly what I was hoping it to do: automatically disable JavaScript on sites unless the domain I specify is listed (called whitelist in this case). You can also allow subdomains per each listed domain so it will work across an entire site. Alternatively you can set the default behavior to work vice versa and always allow JavaScript to work on all sites unless a domain you specify is listed (called a blacklist in this case). Some nitpicks I have (by which I think these functions or abilities would be nice to have but don't hinder functionality currently) are:

Ability to backup and import domain lists within the options.
Support for containers.
An option for a "grey list", or ability to allow JS for the current session/tab/domain but disable again when the browser is closed without need to modify the white/blacklist.

Overall, a great Firefox extension, I highly recommend giving it a try.