Here you are, clear and usefull: Developer Tools extension to auto save script/css files to SharePoint on the fly.


GIF usage sample (click to see)


It is the quickest way to change and test content files of your SharePoint App. 
In addition it might be a good opportunity to fix some js/css bugs without need to deploy scripts using Visual Studio or provide new package of the app.

Key features:
  •  Cntrl+s forces js or css to be rewritten.
  •  Allows modifying SharePoint 2013 App content from the host web
  •  Allows to automatically check-out js/css documents if "Require documents to be checked out before they can be edited" option is True.

Supports SharePoint 2010+ (JSOM).

Next steps will be to publish it to GITHub, I`m open to any comments and suggestions.
I hope this simple tool will save your time!

Thanks!