Is it possible to find out the PID, if such exists of the Mozilla browser process which launches Javascripts?

Oddly enough have just now had to turn off Javascript, because while browsing the main page of this forum, memory usage went ballistic, swap jumped 300 MB and CPU 100%. All froze until browser came up with option to stop unresponsive script, some almost 5 minutes later.

Am fed up with some five minutes after disabling Javascript and minimising browser the whole system freezes due to unresponsive google apis script, best part of 10 minutes system incapacitated.

Flash hogging of system, am able to resolve by killing plugin-container, and it would be great if something similar for Javascript existed. Short of closing browser would like to terminate all running scripts before minimising browser.

try this

example

X-Y-problem!!!

something is clearly wrong with your browser, however that is not the solution.

what system, what distro, what browser (version), what addons?
and are you shutting down your browser regularly and cleaning up local files and do NOT use the restore tabs option?

answer these and we might get somewhere.

also, good you switched off javascript execution for now.
also flash should only be allowed to run after you explicitely allowed it by clicking on it.
addons exist to allow javascript selectively (noscript). a pain to get used to, but worth the effort on low hardware specs.
adblockers also, because besides just sucking, ads also suck resources.

Possibility have been considering. Browser is Light

Linux Kernel 4.9.0, Porteus 3.2.2 KDE5, Light 47.0
Extensions: Another Restart, FEBE, FlashDisable, LastPass, Silent Block, storeTab, (new) disallow Script

No problem here as running in RAM. Only persistence being the browser profile kept on real filesystem.

Something to bear in mind. Been using it on PaleMoon without problem. Could be that here profile has been contaminated. Must try and eliminate that possibility.

Gave up on noscript as one was being asked to make decisions about browser hijacking etc., which presumed expert knowledge of script tricks. Just use Silent Block, as URLs can be specified as regex, meaning sometimes let googleapis through and sometimes block, depending on context of URL. Also have added a user.js to browser profile.

Lastly, funnily enough after posting here got an X Y Solution. Searching for X found Y, being the 'disallow Script', which I thought had fallen by the wayside with FF 44, but apparently still very much alive. This blocks scripts per tab, meaning am able to just allow scripts to run in one tab. Not quite functioning completely properly as it used to do, at the moment, but at least going some of the way. Although providing a partial solution will not deter from quest to find the silver bullet: kill -- -<PID>!

a browser unsupported on most probably ANY linux distro, a larger number of addons, still no info on your hardware.
i see many reasons why your cpu could jump to 100% sometimes.

i don't think the javascript has its own pid, it's just part of the browser process.
but i might be wrong, so keep reading those docs!