JS Bin is a webapp specifically designed to help JavaScript and CSS folk test snippets of code, within some context, and debug the code collaboratively. JS Bin allows you to edit and test JavaScript and HTML (reloading the URL also maintains the state of your code - new tabs doesn't). Once you're happy you can save, and send the URL to a peer for review or help. They can then make further changes saving anew if required.
L. Salucci, D. Bonetta, S. Marr, and W. Binder. Proceedings of the 21st ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming, page 40:1--40:2. ACM, (March 2016)
J. Merelo, A. Garc\'ıa, J. Laredo, J. Lupión, and F. Tricas. Proceedings of the 2007 GECCO conference companion on Genetic and evolutionary computation, page 2851--2858. New York, NY, USA, ACM, (2007)