This is a good, lightweight , new technology Firefox add-on. It is good that it enables or disables JavaScript with one click. But, it is lacking what I consider to be an important option. That option would be to choose if the default action on a new or unclassified web page/domain should be enabled or disabled.

Presently, this extension allows JavaScript by default. Clicking it once toggles that action for all domains that one has not yet whitelisted (in the so-labeled user input field). As soon as you toggle it to allow scripting on any website, it stays that way for all web pages. This could allow a popup, poisoned ad, or JavaScript driven iframe to do its dirty work on a freshly loaded page or site.

So, I suggest adding a user option to deny by default on unwhitelisted sites. This would make browsing new sites a little safer (unless user action to allow scripting revealed a hidden attack!). I would place that option as a right click flyout option on the toolbar icon.

I am only giving it 3 stars because with Firefox 56, it does not honor its whitelisted domains. I have added in a list of approved domains and if I toggle the JavaScript off for a new domain, it stays off for Facebook, Twitter, etc, and all other previously whitelisted domains. This is the opposite of its stated whitelist purpose. If this behavior changes with Firefox 57, I will add one more star.