What is the best approach to make an website like JSBin or JSFiddle? [on hold]

I am an app developer looking to expand into web development. For my first project, I want to make a site like JSBin or JSFiddle.

I know how to make the front end of this app, but I have a few questions about the backend.

The main problem I have is how can do you do the compiling in real time? Do I need a server to do this? I want my app to run in real time.

The second question is how would I format the text to show colors for HTML, CSS and Javascript. Is there a library or a way of doing this?

What would the best framework be for front end in this case? There are lots and what do JSBin and JSFiddle use?

Lastly, as an app developer, I am all about clean code and efficient projects. Xcode usually does the work for me. What are some good tips to make this project clean and efficient from a web developers point of view?

Thanks for your time.