I seem to remember that, in the past, when one disabled Javascript in Firefox, it would immediately stop all previous-loaded scripts and event handlers from running.
However, I am now running Firefox 51 on Ubuntu Linux, and I discovered that setting javascript.enabled to false in about:config still allows already-running scripts to run until the next page refresh.
Is there some mechanism to disable Javascript immediately without reloading the page in modern Firefox?
Best Answer
You can simply go to your dev-tools, in the Debugger Panel, and then click the Pause button || or press F8 :
(screenscast from FF54 on osX)
This will immediately stop all execution of javascript in the current page.