Tengo la siguiente entrada como ejemplo de clubs que incluye una propiedad de players que es una matriz de objetos.

Aporte

 const clubs = [ { id: 5, name: 'Club Name', creatorId: 10, players: [ { userId: 2, // group by this property name: 'Player name 1', clubId: 5, }, { userId: 7, // group by this property name: 'Player name 2', clubId: 5, }, ], }, { id: 6, name: 'Club Name 2', creatorId: 2, players: [ { userId: 7, // group by this property name: 'Player name 3', clubId: 6, }, { userId: 8, // group by this property name: 'Player name 4', clubId: 6, }, { userId: 22, // group by this property name: 'Player name 5', clubId: 6, }, ], }, ];

Quiero groupBy por cada uno de los player.userId s de cada club y debería tener un valor del club para cada jugador, para tener el siguiente resultado.

Salida deseada

 { '2': [{ id: 5, name: 'Club Name', creatorId: 10, players: [Array] }], '7': [ { id: 5, name: 'Club Name', creatorId: 10, players: [Array] }, { id: 6, name: 'Club Name 2', creatorId: 2, players: [Array] }, ], '8': [{ id: 6, name: 'Club Name 2', creatorId: 2, players: [Array] }], '22': [{ id: 6, name: 'Club Name 2', creatorId: 2, players: [Array] }], };

Yo he tratado

 const byPlayer = allClubs.reduce((b, a) => { a.players.forEach((player) => { const id = player.clubId; const clubsByPlayer = b[id] || (b[id] = []); clubsByPlayer.push(a); }); return b; }, {});

Pero devolvió el grupo por el clubId y un valor de cada jugador en el club

 { '5': [ { id: 5, name: 'Club Name', creatorId: 10, players: [Array] }, { id: 5, name: 'Club Name', creatorId: 10, players: [Array] }, ], '6': [ { id: 6, name: 'Club Name 2', creatorId: 2, players: [Array] }, { id: 6, name: 'Club Name 2', creatorId: 2, players: [Array] }, { id: 6, name: 'Club Name 2', creatorId: 2, players: [Array] }, ], };