The grid being those little iframes we show all over the place on CodePen. The homepage, profiles, search results, collections, tags, everywhere. As I page through Recent Pens each day, not a day goes by I'm not locked up by an infinite loop.
We have a URL parameter you can put on any page that will prevent that JS from running. That's pretty useful so you (or we) can get in there and fix it. But it's still not a great system.
JS Bin / Remy Sharp have an open source project called loop protect that they use to prevent this. It's pretty cool and suites their realtime needs well. Our own Alex Vazquez undertook this project for CodePen and ended up going the route of the Abstract Syntax Tree (AST) by way of Esprima.
What isn't quite done yet ...
... is doing this within the editor itself. Alex has some ideas though. It's a bit more tricky because we need to be more careful that we don't interfere too much with your code.
For instance, a
requestAnimationFrame animation is kinda like an infinite loop, and our setup now kinda breaks those. We're working on making it smarter (possibly something testing framerates) so we can get the protection going in the editor itself.
For now, if you get yourself in a bind, remember the URL param so you can get in there and fix the issue.