Heads up! This blog post hasn't been updated in over 2 years. CodePen is an ever changing place, so if this post references features, you're probably better off checking the docs. Get in touch with support if you have further questions.
We were a little behind on the version of TypeScript we were running. There were some newer features that our older version didn't support and it was tripping up some of y'all. Just a quick note to let you know it's updated.
Staying Up To Date
We try and stay up to date on all the preprocessors. We even have a fancy little service to let us know about releases. But we do fall behind sometimes. If that happens, we have an official request form for for updates. We also list the currently running version of everything.
We also moved TypeScript processing to Lambda, Amazon's fancy service where they run your code on their servers and it's all kinds of fast. We talked about using Lambda on Episode 46 of CodePen Radio if you're interested in hearing more about how that works.
Here's a super simple demo of it all working: