Javascript Calculator ok manually but hangs test suite

My JavaScript Calculator appears to work properly / meet all the FCC user stories when I manually input values, but the CodePen FCC test suite just hangs / times out. I have not made my CodePen projects public, so don’t know if the following URL will work: https://codepen.io/OldNoob/pen/RwpMoZv. Any ideas?

Its not the test suite… I got it to hang too. I typed 8 x - 8… that hung your calculator. I see you are using for and while loops in some of your operational analysis… I’m guessing in certain circumstances one of them ends up being infinite.

Don’t know if this helps but I got this error in the console when the test are running

"No prev op: num str starts at 0."

Thank you! You’re probably right about an infinite loop being the problem, and your test case should enable me to track it down.

Thank you! I saw nothing at all in the console; must have not started looking early enough. The message you got points me toward a test I can make outside of the test suite, and should at least let me squash one bug.