We have all been there, so don't let it get you down. Interviews where you are expected to code solutions to problems and you're put on the spot are unrealistic as to what you will face in the real world. The pressure of an interview can make us do silly things like forget basic things like closures or methods like setTimeout and setInterval. In an ideal world and situation, you might even question the use of jQuery and instead opt for a vanilla JS solution which shows that you know more about Javascript than jQuery.