It looks pretty good. If I were to put on my picky hat…
The two lets should be consts.
The first one might want to be outside the function so it doesn’t get reallocated every run - but maybe that’s being too picky, and it may depend. The last consonant is an “s”? This won’t work for “zebra”. Wouldn’t it be easier to list the vowels?
str.match(consonantRegex) == null
Don’t use ==, always use ===. I believe there is a possibility that there exists in the wild a situation where == is better, I just think there is a better chance of catching Bigfoot.
Also, the type to which that ternary evaluates is weird - they’re too different things. That seems odd to me. I’d just make it null or something.
I might just do a return [ternary expression] for the end, but that’s subjective.
But still, good work, you solved the challenge. I’m just being nitpicky, like if this were a code review at work.