Open JS Sandbox
A live version of the sandbox is here - https://code.patricktriest.com
Sandboxed iframe execution
This web app is completely self-contained, it requires no server component or API to function. It runs the code within a sandboxed iframe, intercepts console log statements, and sends those logs to the main app.
Note that the code runs within the browser, so watch out for infinite loops, which will freeze the browser tab.
On opening the sandbox, two editor options are presented: Monaco and Ace. The resources for the chosen editor will be download once it is selected. Both editors are open-source, and very high quality. Ace is more lightweight(120kb), whereas Monaco(the same editor as used in VSCode) is heavier (1.4mb) and more feature rich.
This web app is also configured as Progressive Web App (PWA), so on compatible browsers (i.e. not Safari) it will work completely offline.
This web app can be easily embedded in any other page using an iframe, to provide a live JS sandbox within any webpage. For an example, see here - https://blog.patricktriest.com/what-is-async-await-why-should-you-care/