The addon is good but, for Mozilla's fault, the addons have lost power on what they can do (not only this one).
As such, this addon does not enable/disable the javascript flag (about:config, javascript.enable=false) anymore, on the contrary it only BLOCK the execution, and there is a chasm between TOGGLING and BLOCKING.

Toggling JS off means that website can see you don't have JS and it doesn't waste time sending scripts. It also means that the website can adapt itself for browsers without JS so that you can have it working partially or even 100% even without JS.

On the contrary, blocking means the website knows nothing about your browser blocking JS, so:
- The band/time is wasted because it sends the JS script anyway
- the website doesn't work well or at all (try google image: empty page. With a real toggler it was 100% useable without JS).


Result: None of the JS toggler for FF 57+ can really act as a toggler and we have the above problems.

The problem is not of this extension or is a developer fault, the problem is Mozilla Firefox way (and Google Chrome is even worse).