14th September 2021 J3
The Joomla content plugin xbAutosave allows for timed automatic saving of work whilst editing an article or triggering a save with Ctrl+s or Cmd+s keystroke.
The autosave interval can be set in seconds (minimum 30sec) and timed save and keystroke save can be enabled separately.
Autosave only works on the backend (admin) site and only when editing an article (com_content). It is disabled on a new article until you have saved manually to give you a chance to set category, status, access etc before your work-in-progress gets automatically revealed to the world!
This is probably a bug in the Joomla custom TinyMCE package. Joomla TinyMCE usually crashes out of the article editor page when Cmd+S is pressed causing you to loose all your work. If AutoSave is installed then occasionally Cmd+S will save your work, but mostly it still fails. Very annoying but beyond my understanding to fix.
Meanwhile at least AutoSave will mean you only loose the last 30 seconds or so.
Autosave is based on the plugin CtrlS by Chupurnov Valeriy. This hasn't been updated since 2015 and had several problems and bugs. I think I've cleaned up most of them.
Joomla 4 modifications courtesy of Pascal Leconte - chapeau! and many thanks.