trim() is deprecated in the forthcoming jQuery 4

[mrleemon]

I tried your plugin with the Test jQuery Updates plugin which ships with jQuery 4.0 beta, and Polylang throws a trim() is not a function error here:

https://github.com/polylang/polylang/blob/bcc11ff89075b8d483aa17f44458714f8999f890/admin/admin-base.php#L335C74-L335C78

[mrleemon]

This is the list of deprecated functions in jQuery 4:

https://blog.jquery.com/2024/02/06/jquery-4-0-0-beta/

It would be wise to replace them with equivalent vanilla JS functions as soon as possible.

[mrleemon]

WordPress 6.8 will ship jQuery 4.0:

https://make.wordpress.org/core/2024/08/23/updating-jquery-shipped-with-wordpress-to-version-4-0/

[wpsumo]

It would be wise to replace them with equivalent vanilla JS functions as soon as possible.

+1

[manooweb]

Hello @mrleemon,
I will look at the Test jQuery updates you mentioned but I think it's a false positive in this case.
This isn't jQuery.trim() call here (or more exactly $.trim()) but the javascript String trim() method applied to the options.data string.

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/trim

However, thanks to point it to us. We opened a task about jQuery 4.0.

[manooweb]

@mrleemon FYI all of our plugins aren't concerned by deprecated jQuery APIs removed in its future 4.0 release.
What you found is an issue with jQuery 4 in the ajax process.

With jQuery 3, a conversion (any data passed as an object is converted to string) is done before ajaxPrefilter.
Now with jQuery 4, I saw that this conversion is done after ajaxPrefilter. As in Polylang we expects to always have a string (json or not) the javascript trim() fails because we try to apply it on an object.

[manooweb]

The breaking changes introduced in jQuery 4 ➡ jquery/jquery#5197

[manooweb]

As jQuery 4 will be introduced in WordPress 6.8, we decided not to fix the issue in our next release.

What?

The difference between jQuery ajax code in jQuery 3.x and 4.x is that Ajax request data are converted to a string before applying prefilters.

• See in 3.x https://github.com/jquery/jquery/blob/3.7.1/src/ajax.js#L564-L570
• See in 4.0.0-beta2 https://github.com/jquery/jquery/blob/4.0.0-beta.2/src/ajax.js#L565-L571

Note:

• Ajax request data could be PlainObject or String or Array See https://api.jquery.com/jQuery.ajax/
• key/value pair array (associative array) is represented as an object.
• See jQuery.param() for the conversion to string https://api.jquery.com/jQuery.param/

How?

We have 2 options to fix it:

• As jQuery 3.x does, apply jQuery.param() to stringify the ajax request data and then execute our code like now.
• Add a condition to process specifically the PlainObject case and exclude Array