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arvgta

Synchronous loading causing warning

in Using jQuery • 5 years ago

I am developing the jQuery plugin below, and this issue at GitHub was raised by a user .

The plugin is responsible for "throwing" a warning in the console:

Synchronous XMLHttpRequest on the main thread is deprecated because of 
its detrimental effects to the end user's experience.

I attempted to research the possible cause and have ruled out that it is due to a missing

async: true

in the central $.ajax() call.

Next, I've ruled out, that it is due to attaching script tags, as described in here...

I'm now clueless, and wondering what else might be a classic reason for this warning message?

Thanks in advance!

jQuery Ajaxify Plugin: http://4nf.org/

Replies(28)

jakecigar

Re: Synchronous loading causing warning

5 years ago

Without seeing the page that gets the error, I don’t think the problem can be diagnosed. You found the most probably problem.

Can you reproduce the error in some particular browser?

JΛ̊KE

arvgta

Re: Synchronous loading causing warning

5 years ago

Hi Jake,

Thanks!

The error can be seen on all browsers (I think) on one of these sites

(when navigating to another page):

- http://4nf.org/

- http://www.oeko-fakt.de/

To be more precise, the ending of the warning is:

jquery.js?ver=1.11.2:4

jakecigar

Re: Synchronous loading causing warning

5 years ago

It’s not "all" browsers. I loaded both pages in Safari, Chrome, and Firefiox. I see no errors.

JΛ̊KE

arvgta

Re: Synchronous loading causing warning

5 years ago

forgot to add: when navigating to another (sub-) page

jakecigar

Re: Synchronous loading causing warning

5 years ago

D’oh! Switch to a non-minimized version of jQuery. We may find the line that causes the error.

JΛ̊KE

jakecigar

Re: Re: Synchronous loading causing warning

5 years ago

And all other scripts too!

JΛ̊KE

arvgta

Re: Synchronous loading causing warning

5 years ago

Thanks Jake!

Much appreciated!

Yes, it now says (on http://4nf.org/):

jquery-1.11.3.js:9625

The code at that line is:

// Open the socket
xhr.open( options.type, options.url, options.async, options.username, options.password );

jakecigar

Re: Synchronous loading causing warning

5 years ago

It’s not using ajaxify now.

You need to put a stopper before that line to see what options has in it.

JΛ̊KE

jakecigar

Re: Synchronous loading causing warning

5 years ago

url:"http://4nf.org/wp-includes/js/jquery/jquery-migrate.min.js?ver=1.2.1&_=1437239057175" is being requested with async:false

JΛ̊KE

arvgta

Re: Synchronous loading causing warning

5 years ago

it shows the line:

xhr.open(

as throwing the error, when I break the code up into:

xhr.open(
options.type,
options.url,
options.async,
options.username, options.password );

I think

options.async

not being

true

might be the problem?

EDIT:

Yes, exactly - but I thought the default is

async: true

jakecigar

Re: Synchronous loading causing warning

5 years ago

yes. Trace back to figure out why you are loading migrate repeatedly, and synchronously.

The default is true. Time to put on your debugging hat!

JΛ̊KE

arvgta

Re: Synchronous loading causing warning

5 years ago

Thanks Jake!

You helped me bigtime!

I know where to look for now :)

arvgta

Re: Synchronous loading causing warning

5 years ago

The warning can also be seen on this site, that uses the plugin .

(it's hand-made, has really simple and clean HTML and uses an old version of the plugin, called "history")

That rules out, that it is site-specific.

Definitely, the error is being "thrown" by the Ajaxify plugin.

I have also tested setting

async: true

explicitly, once again.

Am clueless again...

jakecigar

Re: Synchronous loading causing warning

5 years ago

I jumped to each page on that site, I don’t see the error.

JΛ̊KE

arvgta

Re: Synchronous loading causing warning

5 years ago

Thanks Jake!

Please see the attached screenshot.

When navigating from the homepage to e.g. the news page, I can see the error, although there are several other errors, too... (tested in Chrome + Firefox)

Attachments

screenshot.jpg
Size : 275.73 KB Downloads : 438 Download

jakecigar

Re: Synchronous loading causing warning

5 years ago

Again with the minimized jQuery! That doesn’t help much. Try cutting back your code to a bare minimum.

JΛ̊KE

arvgta

Re: Synchronous loading causing warning

5 years ago

Hi Jake - thanks!

Much appreciated!

Currently enabled the unminified version of jQuery on http://4nf.org/ this time, without the double "migrate" plugin, but as an override of the other (minified) plugin.

The result is the same as above:

it shows the line:

xhr.open(

as throwing the error, when I break the code up into:

xhr.open(
options.type,
options.url,
options.async,
options.username, options.password );

It would be fantastic to find the line of the error in Ajaxify, the unminified version of which is enabled right now...

(I don't know how to trace back from jquery.js to ajaxify.js)

jakecigar

Re: Synchronous loading causing warning

5 years ago

I put a stop on line 9625… in CHROME!

_iScript = function ($S, PK) {
$("head").append((PK == "href" ? linki : scri).replace("*", $S));
},

The append causes scripts to be inserted.

jQuery._evalUrl = function( url ) {

return jQuery.ajax({

url: url,

type: "GET",

dataType: "script",

async: false,

global: false,

"throws": true

});

};

"<script type="text/javascript" src="http://4nf.org/wp-content/plugins/nofollow-case-by-case/js/nfcbc_scripts.js?ver=0.1" />"

I don’t think there is much you can do about it.

JΛ̊KE

arvgta

Re: Synchronous loading causing warning

5 years ago

Hi Jake,

thanks very much!

Just to wrap up this thread, here just two more links:

(once knowing, this comes from dynamic script insertion - it becomes a "known issue")

- https://github.com/jquery/jquery/issues/2060

- http://stackoverflow.com/questions/28322636/synchronous-xmlhttprequest-warning-and-script

Last question:

Is there a way to suppress the warning, so users of Ajaxify aren't irritated?

I would love to unroot this issue properly, but also see no way of doing so, as the injected scripts should be inserted in the head before the other HTML content...

(e.g. there would be a way of setting

options.async : true

programmatically before the injection, but that would result in undesired behaviour)

So, I agree, that there is nothing that can be done, except maybe suppressing the warning...

Thanks once again!

jakecigar

Re: Synchronous loading causing warning

5 years ago

You can’t suppress the warning. You can remove all the scripts and load them individually and asynchronously. But that may be difficult and problematic.

You could tell people not to use <script src=> in the ajaxed content.

And you can check if it has already been reported as a bug to the jQuery core team.

JΛ̊KE

jakecigar