Pokemon Quest: finding signature moves

const moveUsers = {};

for (const pokemon of app.pokeData) {
    for (const move of pokemon.moves) {
        if (move in moveUsers) {
            moveUsers[move].push(pokemon);
        } else {
            moveUsers[move] = [pokemon];
        }
    }
}

for (const move in moveUsers) {
    let commonAncestor = false;

    for (const pokemon of moveUsers[move]) {
        const evolutions = app.components.pokedata.getEvolutions(pokemon);

        if (moveUsers[move].every( user => evolutions.includes(user) )) {
            // found a common ancestor for all pokemon that learn this move
            commonAncestor = true;
            break;
        }
    }

    if (commonAncestor) {
        moveUsers[move] = moveUsers[move].map( user => user.name );
    } else {
        // no common ancestor found. It's not a signature move.
        delete moveUsers[move];
    }
}

return moveUsers;