If the system encounters any errors, it tries to reboot to fix them. You can disable this behavior.
If your system gets stuck in a boot loop, you can try the following to repair the files you've damaged:
Use a linux laptop with sshpass installed. There may be a way with Windows but go this route if you can. In separate terminal window run a constant, short-interval ping to the car's IP and have the command ready in the second (active) window. You mustn't run the command before you have connectivity to the car or the command will fail. Every boot seems to have a random uptime (up to a few seconds, sometimes none at all) before the connection gets lost and the system reboots.
You may get an error stating "Host key verification failed." To fix it temporarily create a ~/.ssh/config file and insert:
Host * StrictHostKeyChecking no
Set up a constant ping in one window with a .1 second interval. At the default 1.0 second interval, you can waste a lot of time.
sudo ping -i 0.1 192.168.0.xx
Substitute 192.168.0.xx with your car's IP address. If you have a backup of the file, use the following command to restore it:
sshpass -p jci ssh email@example.com "mount -o rw,remount /;cp -f /jci/gui/apps/system/js/systemApp.js.bak /jci/gui/apps/system/js/systemApp.js;sync"
If you do not have a backup of the edited file, you can use 'sed' to repair the file. I would suggest testing your pattern matching thoroughly on a local file first. Here is an example of what worked:
sshpass -p jci ssh firstname.lastname@example.org "mount -o rw,remount /;sed -i 's/What I need to edit/What I need it to be/' /jci/gui/apps/system/js/systemApp.js;sync"