Interview enough people and you'll get people with Masters or PhDs in computer science failing what seem to be trivial problems. Like FizzBuzz trivial. You can find anecdotes on HN and other places...

My own personal worst experience is limited to a Masters in Physics who couldn't code at all, code-like experience was limited to some sort of software tool that some PMs might use to create acceptance tests. Though I think a lot of these cases are just indications of a bigger problem higher up, like HR or the hiring manager not adequately setting expectations of the job role, or just not doing basic screening.

I once asked a person with an MSCS what a string was and they didn’t know. I think it might be a language barrier thing so I asked the difference between an array of characters and a string and again, no answer.

Yes, I'd believe it. At a previous employer, our phone screen was "implement min()" for a long time, and it weeded out way too many candidates.

(My questions have often been tailored around "get the candidate to implement something that would require a for loop" and that is typically enough to start weeding people out, particularly at the phone screen.)

I usually start with, "In JavaScript what 6 values evaluate to false?" ... almost nobody gets it, but it's usually an excellent barometer for how well they know JS as a language and guides the rest of the questions.

Aside: I tend to prefer people who have worked with multiple languages that are different from each other, regardless of language. Also, way too many people look down on JS without actually knowing JS.

... well now I feel dumb, I guessed 5 ... except for false itself!

false, 0, null, undefined, "", NaN

Everything else is truthy. If you think about the original use of JS as mostly input validation, the values above make total sense.