A bit off topic, but I think a good place to ask...
I find jsFiddle pretty limiting for demonstrating anything more than a simple, single document.
- If the fiddle needs some assets - images, etc. sure you can include a complete URL, but then you are obligating yourself to host those forever or else the fiddle becomes useless to others.
- There is no ability to create a multi-document Fiddle.
- There is no way to demonstrate most Ajax, because of cross-domain concerns.
When I started thinking about this, my first thought was some open-source product similar to jsFiddle that one can install on ones own server. But then you are obligating yourself to hosting this forever...
So, I think a better solution is a smarter third-party service.
Asset storage should not be an issue. Storage is cheap today. Maybe the site would have to charge some small fee (like GitHub). I think it could work if they only charge a fee if you want to create some large number of demos, and then anyone can always use and modify for free. So, anyone can create a small number of demos, for a fee you can create a large number, and everybody can always view and modify your demos.
Multi-page is a matter of organizing multiple "fiddles" into a single "project" so should be easily done.
The last part is the ability for the site to proxy Ajax requests (or maybe other requests) to other sites, to simulate single-site Ajax. Now, here, if you provide some Ajax back-end, yes, now you are obligating yourself... But in many cases, that might be a back-end that exists anyway. (Imagine any site that has a public API showing developers how to use it using this tool.) As well, many public API services exist that represent good stand-ins for generic Ajax problems. (maybe need some permission and/or carefully read terms of service...)
Does anything like this exist?
(No, I don't want to write one!)