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"~

wrangler dev seems to work, but wrangler publish doesn't work, gets error "Unexpected token p in JSON at position 0"

I'm trying to make a serverless API using workers, and when I run "wrangler dev" in the command line, the local server is made and I am able to go to the page without error. A json object is shown on the page which is what I think I want since it is a "GET" request.
When I run "wrangler publish" and go to the published site, it says "Unexpected token p in JSON at position 0". I've looked at many links and I cannot find how to see what is wrong. In Cloudflare, the the logs show that the GET requests go through.
Does anyone know what I can do next to try and solve this issue? Thank you!

Figured it out, there was an error when I inspect the page, and I used that in combination with console.logs and the cloudflare worker site to fix the problem

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.

iOS: Javascript code in WKWebView got “query cancelled” error after selecting photo from photo library and before uploading to the server

I use Xcode 9.1(9B55), iOS 11.1 both simulator and real iPhone/iPad.
The website(HTML5+Javascript) I used in mobile safari acts perfectly. But in my iOS app(Objective-C), which uses WKWebView to access the same web page, and set all the "privacy - Photo Library Usage" and others, always got the error below after selecting photo from photo library and before uploading to the server:
[discovery] errors encountered while discovering extensions: Error Domain=PlugInKit Code=13 "query cancelled" UserInfo={NSLocalizedDescription=query cancelled}
But something strange was that I had a successful run for just one time.
I've several threads about this issue, but have no clear solution. Someone said it's a bug of iOS 11.x, but I've tried it on iOS 9.x, the error was same.

I had the same issue on iOS 12.1. I spent a lot of time trying to figure out why I'm getting this error. I thought because of that error I can't upload an image to the server. But turned out on each try, the request fails with 401 status code because of permissions or additional http headers/cookies. In my case, this debug error meant nothing I thought(Maybe that's why additional argument OS_ACTIVITY_MODE = disabled in project scheme worked for other guys, because it just removed debug log from console). So, make sure you have a correct HTTP request with all permissions/headers as well. Maybe it will help you as It helped me. Good luck.

Hosting phono (jquery softphone plugin) dependencies locally?

This may be too obscure a question, but perhaps someone can spot what I'm doing wrong.
Phono (jquery plugin for javascript/flash-based softphone built on top of Tropo/Voxeo) loads a couple of dependencies from the phono.com servers. Namely,
flensed.js
checkplayer.js
swfobject.js
phono.audio.swf
I would very much like to avoid loading these dependencies from an external server (for obvious reasons) and going by this thread on their forums (which I can't register for because it appears every possible username has been "taken") , it should be possible to host them locally.
Here's a prettified source for the main jquery plugin. Maybe I'm just bad at looking, but I could not find a commented, un-minified version either in their full SDK or on github.
So after changing
base_path: "http://s.phono.com/deps/flensed/1.0/"
and
swf: "http://s.phono.com/releases/" + Phono.version + "/plugins/audio/phono.audio.swf"
... all dependencies seem to load just fine, phono successfully grabs a session ID and chats by SIP appear to be working. When I try to dial out or call the session id/SIP, however, I get a javascript error:
Uncaught TypeError: Cannot call method 'start' of null
referring to line 770 : h.start().
this.$flash.play(g, j); appears to return null or undefined. I suck at javascript and can't figure out why.
EDIT - if anyone would be so adventurous as to try this out, you can just grab their "kitchen sink" demo and slap it up on a server without much hassle.

Okay -- this is ridiculous and I'm an idiot for not catching it sooner.
Flash was trying to load the ringtones off my server at the URL that requires authentication. Unfortunately, flash is not a user with a valid session. Hence, flash was grabbing big handful of nothing. Sorry.

You can download the PhonoSDK and all of the samples (including the kitchen sink demo) and run it on your localhost. Here's the link: http://s.phono.com/releases/PhonoSDK-0.2.zip. It's open source, do you can also fork/contribute to the project as well - https://github.com/phono
I just tried it using Apache on my localhost it worked without editing anything.