Develop Reference

JSON Parse error: Unrecognized token '!' - error caught by Sentry

The error in the title is caught by Sentry (an error tracking tool). Below is a screenshot from Sentry - showing the stack trace.
Note: the script /en_US/iab.autofill.payment.js where handleMessage is located is loaded from Facebook (link here), and I couldn't find this script in the javascript bundle, nor anything related to it. I assume it's loaded by a 3rd party script - I'm using Google Tag Manager (which is also loading Facebook Pixel), Segment (loading Hotjar and Mixpanel), and Snapchat. The error started to appear without any changes in these scripts or the services that they're sending data to.
Note 2: It seems that the error is triggered quite often, about 10-15% of the time. I tried to reproduce it but given that it's a handled error, it doesn't show in the dev console.
Any direction on where to look would be much appreciated.

I'm seeing this a lot, and it seems to be coming 100% from users using Facebook browser on iOS (I guess this is the browser you see when you're using the Facebook app).
I tried to debug this with a snippet:
<script>
window.addEventListener('message', function (e) {
console.log(e);
JSON.parse(e.data);
console.log('foo');
}, false);
</script>
This is from the library you linked. Assuming that e.data is JSON string (not e.g. an object?), without any safeguard seems to be breaking things.
The second console.log doesn't fire, so I think this is causing some unexpected behaviours in my case (buttons not reacting to clicks with js listeners etc)
I don't know if there is a workaround or a way to protect from this in Facebook embedded browser (I guess it's loaded there)
Looking forward to hear more info

i have meet that too, its because the one script facebook inject in. will postMessage(Object), but the another script will listen the message and try to JSON.parse an object ,so it will came out a error. u can use 'vconsole' lib, and add a window.addEventListener('message',(e)=>{console.log(e.data)}) and u can see that

Apparently, the issue went away after a couple of weeks without changing anything on my side.

Retrieving console errors to html

My question is different from the other posts similar to this.
AutoCAD offers developers a means of displaying a URL page inside the application. I created an intranet site for my company with the hopes that users can explore via desktop browser or their AutoCAD application.
The problem is that the browser AutoCAD uses is Chrome version 33 (currently its at 84) - there is no way to update or change the browser either.
I have no way to "inspect" or debug the site inside AutoCAD - and I've come to find out there are many difference in v84 and v33. I'm trying to diagnose errors right now but again, I have no way of accessing the console logs inside the AutoCAD Browser.
Is there a way for me to "alert" any errors that the console is trying to give me? (ie: the page can't find a script reference, there is an unexpected '.', etc...)
NOTE - my site runs great on the most updated Chrome browser (v84 on desktop browser), but some little things are not working right in v33 (in AutoCAD Browser).

If you control the website you can attach a listener on the window to listen for any unhandled exceptions. Add this before all other scripts to make sure everything is captured.
window.on('error', (e) => {
// if error is intresting, do work.
alert(e.message);
});
The handler accepts an ErrorEvent object.
NOTE - This will not capture errors that are triggered in scripts across domain. For example if you are loading google maps, and an error is triggered within that script, you will typically get a 'Script error.' and no other info. This has to do with cross origin policies. You can read more here.
If you need to specifically to capture data sent to console.error you can simply proxy the function. This may not capture anything except for code that explicitly calls console.error and is not recommended.
const error = console.error;
console.error = (...args) => {
// alert(...);
error.apply(console, args);
}

Using startTrackPage in Application Insights

I have recently been messing around with Application Insights and have been having a problem with getting the JavaScript API to work. In the default script that you are supposed to add to your page, they use the function trackPageView(). This seems to works, but I had also wanted to gather information about how long a user stayed on the page. I found the startTrackPage() and stopTrackPage() functions and tried to use those to get the information, but I always receive an error from startTrackPage().
Uncaught TypeError: appInsights.startTrackPage is not a function(anonymous function)
I have stepped through the code and the function does not seem to be created at the point I am calling it. trackPageView() is already defined though. I tried calling the function after the document loaded as well and that still failed. However, I can call it from the developer console once the page loads.
Here is where I found the information about startTrackPage() and stopTrackPage() originally. Other than that I have just been perusing around to see if anyone else has encountered this.
I appreciate the help.
Default code from App Insight:
window.appInsights = appInsights;
appInsights.startPageView();
What I have tried:
window.appInsights = appInsights;
appInsights.startTrackPage();
window.onunload = function () {
appInsights.stopTrackPage();
};

Short answer: unfortunately there's currently no way to use appInsights.startTrackPage() in the way you intend reliably.
Long answer: The reason is that startTrackPage() method is only defined in the JS that is downloaded from CDN, so until it is downloaded it is not defined.
What you could do it something like:
appInsights.queue.push(function(){appInsights.startTrackPage();})
however this would not produce correct measurement, because tracking won't start right away.
So your best approach would be record start time manually, however even that you cannot do reliably. First of all you absolutely don't want to use onunload event as at this point it will be too late for Application Insights SDK to send the data so it will most likely get lost. Using onbeforeunload and flush() will help with this problem a little bit:
var pageStart = +new Date;
window.addEventListener("beforeunload", function () {
appInsights.trackMetric("timeOnPage", (+new Date)-pageStart);
appInsights.flush();
});
However even when using onbeforeunload you are looking at high number of potential data losses - you cannot guarantee that ajax request to send data to Application Insights will complete before page navigates away and connection is interrupted. In my testing with IE was getting about 50% of losses.

Facebook like button in site that uses post message spams console

I have a site that uses a lot of postMessage communication between iframes. Putting a Facebook like button in my site causes my debug console to get spammed with messages like
Received message of type object from [domain], expected a string.
This makes development very difficult. Is there any way to prevent this extra logging from occurring? I am new to using facebooks apis so I'm hoping I'm just missing something simple. They can't possibly assume that no one besides them will ever use postmessage.
Thanks!

Actually, disabling console.log is a horrible answer. What if we want to use console.log, but just want to stop the spamming error message? What is causing it? How do we actually fix it?

Actually that's not an extra logging. It's from the Facebook SDK. Simply you can uglify the sdk for removing all console from the library.
1.Download the sdk. https://connect.facebook.net/en_US/sdk.js
2.Uglify it for removing console logging (production version.)
https://github.com/mishoo/UglifyJS
3.Use it in your site.
Another link which may help you:
http://elijahmanor.com/grunt-away-those-pesky-console-log-statements/

You could simply "unset" the console.log function, by doing something like:
console.log = function(){}
Save it in another variable first, for example:
var originalLog = console.log;
Now when the Facebook API tries to use the log function nothing will happen. If you need to use the log function, just enable it first by setting it back to your saved originalLog variable and unset it when you are done using it. Unhandled errors will still show up in your console, regardless of what you have done to the log function.

In my case this was caused by the FVD Video Downloader extension, so maybe you should disable all browser extensions and see if that solves the issue, then enable them back one by one to find the culprit.

appMobi / phonegap setting/deleting cookie click action required 2 times before working?

I can't figure out for the life of me whats up with this. I dunno if this is appMobi/phonegap centric, cause they have there own special ways of setting cookies, and handling them. But I have what seems to be a unique problem overall, and it only occurs in the process of actually writing a cookie for the first time. Or removing it if it exists which is kind of like writing it.
Anyway I have 2 functions that worked perfectly up til the point of introducing the cookies to them. But I need the cookies also as its part of a login check, and a handful of other things. So this is my issue.
I type my user/pass, hit login. get nothing. hit login again, works.
I hit logout after being logged in, nothing works. hit it again.. works..
These are ajax driven functions as well. Dunno if that has anything to do with it or not, but in both cases cookies are being written in one shape form or another and thats when the functions seem to break in respect to the fact that I need to click the buttons that trigger them twice to get the desired effect despite them being a single click action.
If I remove the cookie lines from my functions everything works normally again without problem, with exception that the cookies are required to actually use half the stuff I am building. Also its a lone cookie being written with a numeric value.
Ideas?
AppMobi.cache.setCookie('AutoRemember', uid, 90);
This one line if its there, i have to double click for my functions to work, if its not there my functions work as expected..
a sample of one of my function would be (quickly typing one out here for example sake)
$('#buttonX').click(function(){
url = 'http://www.domain.com';
$.post(url, function(data)
{
if(data.status == "good")
{
AppMobi.cache.setCookie('AutoRemember', uid, 90);
window.location = 'dashboard.html';
}
}, 'json')
});

Ah yes, I ran into the same thing. You'll need to download and init the local_bootstrap.js lib and something from "Develop In Eclipse For Android " (I downloaded the .zip "appMobi Cloud Services library for PhoneGap Android development"). I'm doing the Android app with Eclipse, and I assume you are too, your post didn't mention what IDE you were using.
The .zip file has a great readme.txt on where & what to copy (.java files, jar file, etc.)
found here: http://www.appmobi.com/?q=node/85

Well, come to find out or as far as I can figure at least. This appears to be a glitch between browser and emulator more so than it is my coding. When I run the app in the sandboxed appMobi application from "Test Anywhere" things work as expected all around.
I will be opening up a bug ticked on appMobi where every they take bug reports and I will come back here with a link later so others may follow it as well when and if they come across a similar issue.