Graphic Editor :
Initially JS Designer was created in order to simplify the design process of complex web interfaces that had to be stored in a database (MySQL / Oracle).
If you want to make your interfaces re-useable, highly customisable (skins), multi-lingual, you can either think to an HTML/XML based solution (like many applications using skins), or either think to store all graphical informations in a database.
In this later case, when you call you web-application, a couple of PHP scripts then reconstruct the interface(s) being called by building on-the-fly all necessary HTML and CSS.
With this approach, if you don't want to waste time filling database tables manually with graphical informations, you then immediately need a graphic editor capable of filling the DB for you, while you design your favourite interface with your mouse in a WYSIWYG way.
Code Editor :
The concept of JS Designer has now been extended to the edition of your application code, changing it from a graphical editor to an IDE(still simple although).
This creates very interesting perspectives about application code centralization and re-useability.
Created applications :
JS Designer interacts with the SQL database online (without page reloads), using a small ingenious homebrew js piece of code.
This piece of code, with several others (like dynamic tables handling) can be used in your own DB application.
As no page refresh are needed anymore, you enjoy great response time, just like any other client-side application, but still, it is web-based in the way that your code is centralized & portable.