Fix jQuery.browser is deprecated error after WordPress 5.5 update
Latest update: August 24, 2020 | Reading time: 2 to 3 minutesIf you have updated to WordPress 5.5 recently you may have come across a number of errors like:
https://example-site.com/wp-content/plugins/plethora-featureslib/libs/ReduxFramework/ReduxCore/inc/fields/spinner/vendor/spinner_custom.js: jQuery.browser is deprecated
https://example-site.com/wp-content/plugins/plethora-featureslib/libs/ReduxFramework/ReduxCore/inc/fields/spinner/vendor/spinner_custom.js: jQuery.browser is deprecated
https://example-site.com.gr/wp-content/plugins/essential-grid/admin/assets/js/admin.js: jQuery.parseJSON requires a valid JSON string
Those errors are related to a Javascript tool titled jquery-migrate which is no longer available on the latest version of WordPress.
This tool was created to help migrate away from APIs and features that have been or will be removed from jQuery core. It was included with the previous versions of WordPress for compatibility reasons. It looks like things are moving fast so we came to the point where the migrator has been deprecated itself.
The problem is that some plugins may still need the plugin to work as their developers have not yet released a new version with the updated code.
The solution
WordPress Team released a plugin as a temporary solution. It brings back the migrator so any plugins that still need it, will continue to work until their developers update their code. The plugin is available for free on the WordPress repository.
Just add and activate the plugin and the errors will go away. It will also resolve any related functionality issues.
This solution is valid for all Plethora Themes