Calculator equals bug

I’m trying to figure out why anything happens the second time the equals button is pushed on my calculator. Any ideas? Thanks for any help!

Or rather, why the equation displays “undefined” when nothing should be happening.

This is happening because you have the .normal-button class on your Bootstrap column Divs so when you click on the equals button it is calling the normal-button click function, clearing the equation. Try removing the .normal-button class from the column divs.