It's hard to catch the 'xwiki:actions:save' event before the save request is sent

When you click on the Save & Continue button from any edit mode, the xwiki:actions:save event is fired by actionButtons.js. The problem is that actionButtons.js is adding a listener to this event on xwiki:dom:loaded (which is very early) in order to perform the AJAX save & continue. So by the time you add your own listener from a script that was loaded later (e.g. with Require.js) the actionButtons.js listener was already added so you will be catching xwiki:actions:save after the save request has been sent. This prevents you from updating the content (e.g. serialize some data from a JavaScript widget that you are using).

The current workaround is to attempt to add your listener before xwiki:dom:loaded is fired, but this can be difficult or even impossible. We should modify actionButtons.js to fire a xwiki:actions:beforeSave instead.