How to determine whether a board is a subitem board via the API

[lays (A L)]

Hello!
Let me show you the way how I tried to distinguish regular boards from “subboards”.
This is my configuration:

Let’s perform this query to get subboard’s item list:

query ($boardId: Int) {
  boards (ids: [$boardId]) {
    items {
      id
      name
      creator {
        id
      }
      creator_id
      parent_item {
        id
      }
    }
  }
}

The result is:

As you can see there is a “phantom” item at the first place. You will never see such item in “regular” board. It always has named as “Subitem”, has no creator, has no parent_item (as well as items of “regular” boards) and has unknown id and creator_id. If you try get this item or creator using url (/boards/:subboard_id/pulses/:subitem_id or /users/:creator_id) you will face errors:

So the answer for your question is this js-pseudocode:

const items = response.data.boards[0].items;
let isSubBoard = false;

if (items.length && items[0].name === 'Subitem' && items[0].creator === null) {
  isSubBoard = true;
}

P.S: you can also limit your item list to only 1 item to decrease query complexity using (limit: 1)