Develop Reference

"A listener indicated an asynchronous response by returning true, but the message channel closed before a response was received", What does that mean?

I'm working on a React application and I use some npm modules, one of which I had to build myself. (my NPM package:
https://www.npmjs.com/package/modale-react-rm).
It is a simple modal that opens and closes with a useState().
After importing my package, I have an error in my console that appears suddenly after a few seconds without performing any actions.
Uncaught (in promise) localhost/:1
>{message: 'A listener indicated an asynchronous response by r…age channel closed before a response was received'}
message: "A listener indicated an asynchronous response by returning true, but the message channel closed before a response was received"
>[[Prototype]]: Object
>constructor: ƒ ()
>[[Prototype]]: Object
/* sometimes there are specific elements in addition but I could not check when they appear and when not */
Promise.then (asynchrone)
(anonyme) #content_script_bundle.js:108
handleNewFeatures #content_script_bundle.js:101
handleUpdatedNodes #content_script_bundle.js:101
(anonyme) #content_script_bundle.js:101
childlist(asynchrone)
0 #purplebox.js:1
(anonyme) #purplebox.js:1
v #purplebox.js:1
It doesn't block my pages, nor does it prevent the proper functioning of its features, but it's an error and I think it should be fixed and maybe help other people who have the same problem.
I specify that I do not make any async request in this project. Everything is local and the few data I use are directly imported in raw.
I don't know where Purplebox.js comes from as well.

This issue is a cross-origin request issue and it is caused by various Chrome Extensions.
I had this too in my Angular app and after testing it in the incognito mode, the error didn't show up anymore.
More info: Google Forum
/Edit:
If you are an extension developer coming here: You need to return true when fetching data from cross-origins. More info: Chromium Project

In my case, it is caused by Ghostery extension, if this error appears in your local host, you need to add it to the trusted sites list of Ghostery and the error will be gone.

It has been discussed in the webextension-polyfill library, which is used by many extensions (including Ghostery). There was a recent change in Chrome that introduced to the error message.
For projects that are using the polyfill, I would expect the warning to go away if a fix is merged. Note that the polyfill library is used, since only Firefox implements the new promised-based runtime.onMessage, while Chrome still enforces the original callback-style API.
Note that there is an open pull request in the webextension-polyfill library already. It has not been merged, but according to my tests, it solves the problem. So, if you need a quick fix for a project that uses the library internally, you can manually apply the patch with patch-package. For instance, this is how such a change would look like in Ghostery.

The background script (service worker in MV3) could be going to inactive state without sending a response back to a message it received from a content script.
Example:
Background script:
chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
// ... handle message
return true // Error message says you already return true
})
Most MV3 APIs are asynchronous and can return promises when it makes sense to do so. (In some cases, like event listeners (e.g.: chrome.tabs.onRemoved), returning a promise wouldn't make sense). Reading a response back however can be done using callbacks or promise-style.
Content script: method 1 to read response:
chrome.runtime.sendMessage('ping', (response) => { /* read response */ })
Content script: method 2 to read response:
chrome.runtime.sendMessage('ping').then(response => { /* read response */ })
The issue you are facing is this: background script does not invoke sendResponse() for one/more messages it received and went inactive (causing the message channel to close). However, the content script that sent the message is waiting for the response.
Please check your message senders & handlers.

I had the same error. I removed the Tampermonkey extension and tweaked my AdBlock extension and then it worked for me.

I encountered the same issue couple of days ago, and found out that the source of error is located in the background.js.
it's caused by the runtime Message Handler. to solve it, just add a third parameter as a callback function to chrome.runtime.onMessage.addListener.
forgot how i found the solution, but it works for me.
// to avoid the error, the parameter [sendResponse] is necessary!
chrome.runtime.onMessage.addListener(function(msg, sender, sendResponse) {
// do something ...
// this line seems meaningless but you have to invoke it to avoid error.
sendResponse({damn: true});
});

This error is related to ad blockers or similar. Just exclude the site for this application.
In my case it was AdBlock app. It kept showing this error in the console when working with LiveServer or FiveServer. It does not affect anything, but it is very annoying

I had the same error on my react app when i introduced an infinite loop through useEffect, the thing is that you most likely won't see too much change in your app or problem. For me it even helped reload some state for functions that i was still to write but over time it will introduce bugs and performance issues.

Avast Online Security & Privacy 22.11.173 is causing the same issue.

I had the same issue on my Windows 11 machine.
I added these lines at the bottom of the hosts file in the drivers/etc directory:
127.0.0.1 localhost
::1 localhost
This solved the problem for me.

I faced the same error. Where class Component didn't show any response over display.
Solution : Syntax error in spelling "render" => ~"rendor"~

Occasionally getting Reference Error in Javascript console

I am occasionally getting different types of Reference errors logged in chrome console.
For eg: require not defined
Cookies not defined
lozad not defined
The code is bundled in static-internal-bundle.js which is a combination of 7 different util files and minified using gulp-minify.
This error is coming mainly when the url is hit from paid.braintree.com Ad urls and has utm_source, utm_medium and utm_campaign as query parameters.
This error is not consistent and mostly does not reoccur if the site is refreshed.
Also, it has been logged in sentry for all types of devices and Os for over 1.5k times in 6 months. Though it gets logged in console, nothing seems to break on the webpage.
What could be the possible reasons for this type of error?
<script type="text/javascript" src="https://static.pens.com/576801d7b3a368c06ba1944c07fe260b970da596/build/static-internal-bundle.js"></script>
This is the script that gets added into the page in which the error is coming.

I would add this as a comment but StackO won't let me without 50+ rep... I'll edit as needed.
Possibly the error could be in using "require" on the browser side, as browsers do not implement require
This sounds like a problem I have had with Babel, if it is being used I would try updating.

Web Component: Dom Exception: This name has already been used

tl:dr; I don't know how to fix the error below on the site here:
You will need credentials:
un: stackoverflowuserj23jf4#mailinator.com
pass: testingStackOverflow123
Details: I am trying to conditionally include a web component in a page like so:
<script>
document.addEventListener("DOMContentLoaded", function(event) {
if (document.querySelector('simple-fred')) {
var script = document.createElement('script');
script.src = 'https://embedint.crossroads.net/fred/js/simplefred.min.js';
document.head.appendChild(script)
}
});
</script>
Including the script conditionally instead of statically broke the code. The script above used to be loaded like this:
<script src="https://embedint.crossroads.net/fred/js/simplefred.min.js"></script>, which worked
I then include the element on the page:
<simple-fred data-form-name="buildingblocksformarriage" data-redirect-url="/care/weddings/building-blocks-for-marriage/signup/confirmation"> </simple-fred>
This works fine locally and on plunker.
To run it on plnkr, you do need to disable CORS blocking for Chrome, the command is:
TASKKILL /F /IM chrome.exe
start chrome.exe --args --disable-web-security --user-data-dir
pause
This is all good and well, but when I run this code in concert with other code, it fails. I get the following error (same error, browsers report it differently):
Chrome:
Uncaught DOMException: Failed to execute 'define' on
'CustomElementRegistry': this name has already been used with this
registry
at Function.value (https://embedint.crossroads.net/fred/js/simplefred.min.js:5:383105)
Mozilla:
Error: A custom element with name 'slim-repeat' has already been
defined.
This error seems to be caused by two third-parties trying to create the same custom component as far as I can tell judging by this question I have a bounty on
I am at a loss at this point. The int environment that throws the error is here:
https://int.crossroads.net/care/weddings/building-blocks-for-marriage/signup
You may need a login, I made one so it's faster (can be shared):
stackoverflowuserj23jf4#mailinator.com
testingStackOverflow123
The code is open source and is found here (I don't think looking at it will help, just for completeness): https://github.com/crdschurch/crds-fred/blob/development/CrdsFred/Views/Form/Index.cshtml
How do I fix this?
Or at least, what are possible causes? I will throw at least a 100 point bounty on this to reward the accepted answer.

it looks like there's a node module named slim-js, and it creates an element called slim-repeat on lines 1057 and/or 1146 of Slim.js (see screenshot). Maybe you just need to pick a different name?

I am the author of this library and would like to assist. I will deploy a hot fix for this Issue. Eventually not running the whole script if another instance of Slim is already initialized.

Log JavaScript console into a log file with Firefox

We have a web application which runs in a kiosk mode Firefox, using the RKiosk extension to achieve this. We suspect that we have a very rare error in the system which yields in a JavaScript error. However because we can't access the JavaScript console we can't examine the log.
I'm searching for an option to make Firefox log all JavaScript console messages into a file regardless of the tab and page opened. I can't seem to find any extension for this. I'm already using log4javascript which sends errors back to the server, but it seems that our application crashes in a way that it skips the logging altogether.

Writing to a file sounds like a tedious task to me. It requires privileges that browser code doesn't normally have and you'd have to negotiate with an add-on you'd have to write in order to access file I/O.
From what I understand your issue is
I'd like to make Firefox log all errors
There are several approaches we can do to tackle this
First approach - log everything to localStorage too:
Now, rather than writing to an actual file, you can write to localStorage or IndexedDB instead.
localStorage["myApplog"] = localStorage["myApplog"] || "";
var oldLog = console.log;
console.log = function(){
oldLog.apply(console,arguments); // use the old console log
var message = "\n "+(new Date).toISOString() + " :: "+
Array.prototype.join.call(arguments," , "); // the arguments
localStorage["myApplog"] += message;
}
This is rather dirty and rather slow, but it should get the job done and you can access the log later in local storage. LocalStorage has a ~5MB limit if I recall correctly which I think is enough if you don't go crazy with logging. You can also run it selectively.
Second approach - log only errors
This is similar to what Pumbaa80 suggested. You can simply override window.onerror and only log errors.
// put an empty string in loggedWinErrors first
var oldError = window.onerror || function(){};
window.onerror = function(err,url,lineNumber){
oldError.call(this,err,url,lineNumber);
var err ="\n Error: (file: " + url+", error: "+err+", lineNumber: "+lineNumber+")");
localStorage["loggedWinErrors"] += err;
}
Third and drastic approach - use a VM.
This is the most powerful version, but it provides the most problematic user experience. You run the kiosk in a virtual machine, you detect an uncaught exception - when you do you freeze the machine and save its state, and run a backup VM instead. I've only had to do this when tackling the most fearsome errors and it's not pretty. Unless you really want the whole captured state - don't do this.
Really, do the extension before this - this is tedious but it gets very solid results.
In conclusion, I think the first approach or even just the second one are more than enough for what you need. localStorage is an abstracted storage that web pages get for saving state without security issues. If that's not big enough we can talk about an IndexedDB solution.
It all really depends on the use case you have.

You can use XULRunner...a Mozilla runtime environment for XUL applications. It uses Gecko like Firefox and:
You can access the file system or using the SQLite database to store logs.
You can render your kiosk in fullscreen mode without using extensions.

Have you tried jserrorcollector? We are using it and it works fine (only in Firefox). It's only for Java.
// Initialize
FirefoxProfile ffProfile = null;
ffProfile = new FirefoxProfile();
JavaScriptError.addExtension(ffProfile);
// Get the errors
List<JavaScriptError> jsErrors = JavaScriptError.readErrors(webDriver);
More information: https://github.com/mguillem/JSErrorCollector

Have you considered remote logging?
I commonly assign window.onerror to do send a request to a webserver storing the details of the error remotely. You could do the same with console.log if you preferred.

Try the following console export. It is a plugin for Firebug of Firefox. It's quite handy.
http://www.softwareishard.com/blog/consoleexport/

If you are able/willing to switch from Firefox to Chrome or Opera you would be able to use the Sandboxed Filesystem API to write a local file. See:
http://www.html5rocks.com/en/tutorials/file/filesystem/
http://caniuse.com/filesystem
Start in kiosk mode using chrome.exe --kiosk <url>
You would then want to disable Alt-F4 and Ctrl-Alt-Del which on Windows can be done with several third-party tools like Auto Hotkey (Disable Ctrl-Alt-Del Script).

You could use a remote logging script like Qbaka. It catches every JS error and sends it to the Qbaka server. There you can login and see all JS errors. Qbaka stores the exact error message, the script, line number, stack trace and the used browser for each error message.

Crm 2011 with no javascript customizations gives onload errors

we are getting the following error in almost all create or edit entity forms. the systems is not customized at all and it works perfectly:
There was an error in the fields customized event.
field:window
event:onload
error:object doesn't support this property or method
after debugging the error I found out that it is happening in FormScript.js.aspx page in the following code block:
var eContext=Mscrm.FormUtility.constructExecutionObject(eventObj,0,null,null);
eContext=Mscrm.FormUtility.constructExecutionObject(eventObj,0,null,eContext)
Mscrm.Form_onload();
Mscrm.Form_onload() is what causing the error to happen.
do you have any idea why is this happening?

It was a server side problem. I don't know exactly why it happens. we also tried to do an installation repair but that didn't solve it. Finally, we installed a fresh CRM 2011 copy on a new server, imported the database and ran Data migration manager. and the error disappeared.

Are you absolutely positive there is no script attached to run on load of any of the entities that are having issues? That particular function should just run any custom script you have on the entity, so I don't see any other cause.

Odd, there is certainly some garbage in there somewhere
function crmForm_window_onload_handler(eventObj,eventArgs){
try{
var eContext=Mscrm.FormUtility.constructExecutionObject(eventObj,0,null,null);
eContext=Mscrm.FormUtility.constructExecutionObject(eventObj,0,null,eContext)
loadInsideView();
eContext=Mscrm.FormUtility.constructExecutionObject(eventObj,1,null,eContext)
CEI.Initialize();
} catch(e) {
displayError('window', 'onload', e.description);
}
}
Here is one from our system on the account form. I have no idea how this could have happened, but I would check the events for the page (not just the onload). I would also try adding a JavaScript web resource with a generic event to the onload to see if by toggling it on, the system might clean itself up. You may have to call Microsoft or find the issue in your 4.0 and fix it to do another re-install. I feel for you on this one!