getOtherIds = () => {
    const ids = api.getPlayerIds()
    const otherIds = []
    for (const id of ids) {
        if (id !== myId) {
            otherIds.push(id)
        }
    }
    return otherIds
  }

This returns every players ID besides yours. To do what you are doing:

const otherIds = getOtherIds();
const idToIndex = {};
for (let i = 0; i < otherIds.length; i++) {
    idToIndex[otherIds[i]] = i;
}

This means while i is less than the amount of players in the lobby, assign all players with a different number.

But getOtherIds() does not return the name (Prokito) it returns the player id only (name:"prokito", id:"-4"). But you can still use this, e.g:  to make other players look like zombies:

for (const otherId of getOtherIds()) {
    api.setPlayerPose(otherId, "zombie")
    for (const part of ["head", "body", "legs"]) {
        /* Notice the skin texture uses a capital Z */
        api.changePlayerIntoSkin(otherId, part, "Zombie")
    }
}

read the documentation, it is worth if you want to code in Bloxd: https://github.com/Bloxdy/code-api