Question

My Java is up to date too

Guys, the problem is most likely with some of your plugins. I started FireFox in safe mode with all my plugins disabled (menu Help) and the problem with JavaScript syntax error disappeared.

This issue can be caused by an extension that isn't working properly.
Another user has reported that the Social Fixer extension caused this issue.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do not click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Same issue with latest upgrade. In Safe Mode removed SocialFixer. That fixed the problem.

I have the same problem but it happens on pages that are not on facebook, (like pages on Oprah.com) which tells me its NOT socialfixer, or not JUST to do with socialfixer.

My java is also up-to-date.

I was getting the Syntax Error (Javascript ap.) in Gmail (Start Page). After disabling Integrated Gmail 2.8.8, All back to normal !

I still have the problem. Is there a way that Firefox can fix the problem from their end, for those of us who aren't that technically savvy?

I would like you to first try Safe Mode. Do not confuse this with Windows safe mode. Read here: https://support.mozilla.org/kb/Safe+Mode If you can operate your browser, you should be able to get into Safe Mode. Reading is knowledge, thus read the link first. Once you achieve Safe Mode, report back to us on the forum with your results. Good Luck!

Thanks, DriftMGR, for contacting me so quickly. I clicked the Restart Firefox button. Now everything looks very different, but happy to say that Error Message isn't popping up all the time anymore. May take a while to adjust to all the other changes, but I will manage. Thank you

Ok, so it turns out that for me it really was socialfixer. There was an upgrade on Tuesday and I just found out about it today. All better for me.  :)

Now my Adblock isn't working anymore. Groan. That has always been one of my favorite things about Fire Fox. No ads. Any advice on how to get Adblock working again?

Hi summertime

Try to ask advice at the Adblock Plus forum.

• https://adblockplus.org/forum/

46 views and 0 answers on the Adblock Plus forum :-(

Social Fixer was the culprit in my case. The problem has been fixed in their version 7.3.

Same problem (and solution) here with the syntax errors happening not only on facebook, but other sites like IMBD etc.

Social fixer was the problem and updating it resolved the issue, the version available via the Add-ons Manager is still the old one but the version available from the socialfixer.com is working fine.

@ summertime, FWIW I'm using ABP without issue.

Thanks people.

I changed to Safe Mode and It solved the problem. But how can I discover wich plugin (or plugins) or extension is causing the problem? thanks in advance.

With all plug ins disabled, you can add them back one by one. Restart when needed. Continue this process until you find the non-compatible plug-in.

Ok, and I discovered that the extension that was producing the error message was "Linkify (for Microsoft Lync) 1.0. I I excluded it and I didn't receive the error message longer. Thanks for the help. Very very thanks. Antonio Carlos.

google social fixer 7.3 and download it. fixed the problem for me as well.

I don't know what is this App the "google social fixer". Where can I download it from where?

http://socialfixer.com/ just choose the browser you use and it'll download the application

You only get this 'Error: Syntax error' from JavaScript application notification if you have an extension installed that isn't working properly and is responsible for this error.
There is no need to install an extension.

Other extensions may be causing a similar error to appear, so check that if you do not have the Social Fixer extension.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

I had an gmail third-party extension that caused the Javascript syntax error. This is how I tracked it down in amongst all the other addons. 1. Go Start and enter Run. 2. Enter -firefox -same-mode. 3. On the dialog box displayed, click OK and Firefox will start in Safe Mode. 4. Check if the problem has disappeared. 5. If not, in Firefox go Tools > Options. . 6. On the General tab, click the Manage Add-Ons. 7. Disable all the add-ons, restart Firefox to see if problem fixed (in my case it did not fix the problem. If the problem has been fixed, progressively enable the add-ons until you find which one caused the problem. 8. On the window displayed when you click Manage Add-Ons, select Extensions in the left-hand menu. 9. Do as above and disable all the extensions. 10. My guess is that the problem should now have disappeared. 11. Finally, progressively enable 2-3 extension until you have isolated which one has caused the problem.

IMPORTANT. After each enable/disable operation, you needto restart Firefox.

I've recently started having this problem on a system which does not have Social Fixer. What is the difference between restarting in Safe Mode and disabling add-ons? If I restart in Safe Mode I don't have the problem, but if I disable all add-ons I still do.

How do you re-enable add-ons in Safe Mode? As I understand it, all add-ons are completely disabled until the next restart.

Just to add an extra detail. I still get just as many Java Script errors if I disable Java Script.

@Maryxxx. Hopefully, I am sure Mozilla support will answer your question better than I can. My understanding is that Safe Mode only prevails for your current session. If you restart Firefox, it starts in normal mode.

If you still have the problem after disabling all the add-ons, I suggest you also disable the Extensions as I described in my earlier post. This is how I was able to isolate which extension caused the problem.

If you disable JavaScript via "Firefox > Options" then that only effect JavaScript used on web pages, but it has no effect on extensions and internal Firefox JavaScript files.

You will have to click the Disable button next to each extension on the Tools > Add-ons > Extensions (about:addons) page and close and restart Firefox.

If it works in Firefox Safe-mode then disable all extensions (Tools > Add-ons > Extensions) and then try to find which is causing it by enabling one extension at a time until the problem reappears.

Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

"Disable JavaScript only affects web pages". OK, got it now - that isn't clear from the options/add-ons/plugins pages. I might have forgotten to restart on some occasions too.

Upgrading Social Fixer from 6.6 to 7.3 seems to have solved the problem on all VMs and hardware systems that have Social Fixer on them. If I can reproduce the problem on a VM without it I'll go one add-on or plugin at a time and try to find another culprit.

Postscript: I have not been able to demonstrate another culprit, so I'll stick with the "Social Fixer v6" explanation.

I had this problem on 17.x and 18.0; adblock plus didn't seem to be the problem, since alternately enabling and disabling everything for FB didn't help.

Per the advice elsewhere on this thread, updating Social Fixer (which wasn't showing up at all on FB, so I had assumed that I'd already disabled it on this laptop and it couldn't be the problem) solved the problem. You can find the most current version at http://socialfixer.com/ .