We came up with the idea when we were building the checkout process for thoughtbot books. Whenever someone buys one of our books they need to be added to the corresponding GitHub repository for that book. If they enter an invalid GitHub username we want to be notified via email so we could follow up with them directly. It seemed like overkill to build and deploy an entire app just to make some GitHub API calls and send some emails.
Use JSbox Beta at your own risk. It is unclear whether running untrusted code inside a Docker container is safe. We’re using it in production and haven’t had any issues. If enough people find JSbox useful we will continue to develop it. If it continues to prove useful we’ll take it out of beta and begin charging for it. Head over to JSbox.io and let us know what you think!