Are there ready-made implementations of a two-level drop-down list (tree) in JavaScript?

Question

JavaScript

Good afternoon, dear JavaScript gurus
, can you please tell me if there are ready-made implementations of a two-level drop-down list (tree) in JavaScript? So that the script can save the entire tree to the database via REST and, if necessary, receive a list from the server?

Answer 1

it's done by hand...

Answer 2

In any case, you yourself will have to determine how to transfer and store this data, so it's easier to write with pens than to adapt to a ready-made solution.