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);
}

Webextension inline install chrome.runtime.connect issues

I'm having a really weird issue, I've developped a webextension that uses messaging between content script and background script (using chrome.runtime.connect) and nativemessaging.
The issue i'm facing is that when I install the extension (manually from the store beforehand and then connect to my website, everything works as expected, the chrome.runtime.connect works and returns a valid port to the background script.
But when i do an inline install of the extension from my website to get around the fact to have to navigate to have the content script in the webpage, i manually inject the content script into my page using
function injectContentScript() {
var s = document.createElement("script");
s.setAttribute("src", "chrome-extension://<extensionid>/content.js");
document.head.appendChild(s);
}
and the exact same content script but manually injected doesn't behave the same. chrome.runtime.connect returns a null object and chrome.runtime.lastError gives me
Could not establish connection. Receiving end does not exist.
I'm calling on the sender side (content.js - manually injected content script) chrome.runtime.connect(extensionID) where extension id is the id of the extension generated by the chrome webstore. And on the receiving side (background.js - extension background script) chrome.runtime.onConnect.addListener(onPortConnected);
I'm not really sure how to debug this issue, maybe it's a timing issue?
The background script is well executed even with the inline install (i've added logs and debugged it through the background.html in chrome extension manager)
Any help would be greatly appreciated!

You have two scenarios.
Your content script content.js is executed as normal upon navigation, as a content script defined in the manifest.
In this case, it executes in a special JS context attached to the page and reserved for your content scripts. See Execution Environment docs section for explanation. It is isolated from the webpage and is considered part of the extension (albeit with lower privileges).
When you connect from a content script, chrome.runtime.connect() is treated as internal communication between parts of the extension. So while you can provide the extension ID, it is not needed.
More importantly, the event raised in this case is chrome.runtime.onConnect.
Your supposed "inject content script immediately" code called from the webpage does something completely different.
Instead of creating a new execution context, the code is instead added directly to the page; it is not considered part of the extension and has no access to extension API.
Normally, a call to chrome.runtime.connect() would simply fail, as this is not a function exposed to webpages; however, you also declared externally_connectable, so it is exposed specifically to your webpage.
In this case, passing the extension ID is mandatory for the connect. You were doing this already, so the call was succeeding.
However, and that's what made it fail: the corresponding event is no longer onConnect, but onConnectExternal!
What you should be doing is:
Not mixing code that is run in very different contexts.
If you need communication from the webpage to background, always do it from the webpage, not sometimes-from-content-sometimes-from-page.
That way you only have to listen to onConnectExternal and it cuts out the need for a content script (if it was its only function).
See the docs as well: Sending messages from web pages.
You don't have to source the code from chrome-extension://<extensionid>/; you can directly add this to your website's code and potentially avoid web_accessible_resources.
And if you actually want to inject content scripts on first run, see for example this answer.
Related reading: How to properly handle chrome extension updates from content scripts

How to detect and display Javascript error from AJAX call in Chrome DevTools

I have a Rails app that receives form data and renders some Javascript. Here is an example of such a response:
The Rails app generates the Javascript without error and serves it with the correct content-type and a status code of 200. So on this tab in the DevTools there is no apparent error.
However, there is an error in the Javascript itself, namely an undefined function:
As you can see, I have "Log XMLHttpRequests" turned on in my DevTool settings. Javascript errors triggered from page events appear in the Console as expected, but Javascript errors from AJAX calls don't. The only way I can discover that there was an error in the returned Javascript is to copy/paste the code from the response into the Console.
This seems like a pretty critical feature that just doesn't exist. Am I missing something or is this simply not possible with Chrome DevTools? If so, is there a workaround to this problem that would fit into my workflow?

Replacing entire page via AJAX causes Permission Denied error in IE only

I have an AJAX post that retrieves data from the server and either replaces part of the page or in some cases the full page. This is controlled by a javascript fullRefresh parameter. The problem is the refresh code works find in Firefox but causes a Permission Denied error in the bowels of JQuery after it runs in IE although it would appear to actually replace the page contents successfully.
IE version 11.0.9600.16659
JQuery version 1.8.2
Error message
Unhandled exception at line 2843, column 3 in http://localhost:62761/Scripts/jquery-1.8.2.js
0x800a0046 - JavaScript runtime error: Permission denied
My code is
function RefreshScreenContent(formActionUrl, formHTML, fullRefresh) {
fullRefresh = (typeof fullRefresh === "undefined") ? false : fullRefresh;
if (fullRefresh) {
document.write(formHTML);
document.close();
}
else {
$("#content-parent").html(formHTML);
}
}
The partial refreshes work fine but the full refreshes are the problem. I have tried hardcoding the document.write call to write a well formed simple html page rather than formHTML in case that was somehow the problem but even a simple single word page causes the error.
The actual error occurs a some point later with a callback inside JQuery.
The AJAX post to the server is in the same application i.e. is not a cross domain request. I have seen posts online talking aboue cross domain stuff that is not applicable here.
Can anyone tell me why this is happening and how to stop it? Is there an alternative IE way of replacing the page contents?

Your code is fine (at least at first glance). My guess is that you make the call in such a way, that it is interpreted as cross-domain.
I would suggest checking:
http vs https (most common)
the destination port
the root url
maybe the "destination" page makes some requests of its own, check to be on same domain
The reason why IE may be the only one with the problem is that it has higher security demanding by default that other browsers (check advanced security settings - can't remember where they are put in menu) so it interprets requests in a more "paranoid" manor.
I repeat, what I said is just a guess, based on cases I've been put into.

In the end I used the approach here to replace the body tag in the pgae with the one in the markup the AJAX receives back https://stackoverflow.com/a/7839921/463967
I would have preferred to replace all content not just the body but I can always adapt later to include the header etc as body is enough for my uses right now. This works in IE and Firefox.