I felt that the interview process really emphasized esoteric knowledge that requires exact memorization. If you don't know the concept (which is never used in real life), you're screwed.

One question was to implement JSFiddle using iFrames, which I hadn't studied.

Apparently, part of the key code is:

javascript const frame = document.querySelector('#iframe-window').contentWindow.document;

If you haven't memorized the exact syntax "contentWindow.document," you basically fail because you can't write anything into the iframe. (Also, there's more esoteric code you have to memorize to complete the problem).

Do they expect me to just write all this from memory? I thought it was an unreasonable expectation.

Implement debounce.

In the JSFiddle example, put the CSS on the bottom left and the HTML on the top left.

(How in the world are you supposed to do that? You can't put CSS anywhere!)