We’ve recently been updating sites to WordPress version 5.5.3 and 5.6. We’ve come across a few errors and we’re going to log them here so that we can share any useful advice for our clients and readers.
jQuery Index Of … – Warning / Error
Go to your theme’s JS folder and look for the minified JS file and change the following:
Slick Slider not working
Slick Slider and Autoptimize
If you use Slick Slider and autoptimize and update to 5.6, it’s likely that you will run into an issue with the slider not being styled correctly. To fix this go into the autoptimize settings and turn OFF Aggregate JS files.
Installing “Enable jquery migrate helper” plugin
This plugin will allow you to pick which jQuery version is used by jQuery on WordPress 5.6. It also can log errors that occur in both backend and frontend. The options available in this plugin are:
You can only change jQuery versions in WordPress 5.6 or later
Show deprecation notices, on each admin page, as they happen
Public deprecation logging
Log deprecations caused by anonymous users browsing your website
Caution: This option may lead to more deprecations being discovered, but will also increase the amount of database entries. Use sparingly and under supervision.
WordPress admin plugin settings
We’ve noticed a few issues on the backend while updating to 5.5 and 5.6. Some plugin “Settings” pages have not appeared correctly, and some widget/sidebar settings also have had display issues. This can sometimes be rectified by using “Enable accessibility mode” in the widget settings area, however “jquery migrate helper” may be required to get all widgets working properly. The most common issue has been browsers saving cached versions of old jquery.js, so deleting browser cache is always the first thing to check if experiencing wp-admin problems.
We’ve seen some themes that have various issues on WP 5.6, e.g. many have had the mobile menu break when moving to WordPress 5.6 and using the new jQuery version. The easiest fix for this is to ensure the theme is updated to the latest version. If there is no recent update for the theme, then manual editing of theme files will be required.
It is advisable to export theme settings before updating a theme, as you will be able to reinstate any lost settings that may occur during the update.
Update all plugins
Make sure to update your plugins as many will have updates that introduce support for the new jQuery version.
Let us know if you have any tips and advice for resolving WordPress jquery errors.