I am relatively new to JavaScript, though not to programming, and
I'm having trouble finding the idiomatic JS solution to the following
problem.

I have a table with (say) fields f1, f2, f3. I do a database
query and what I wind up with is a structure Q of arrays:
Q.f1[n] is field f1 in row n,
Q.f1.length == Q.f2.length == Q.f3.length is the record count of the query.
(This representation is of course...