Using polkadot.js api, how can we list the members of a Kusama nomination pool?

Question

According to the documentation, api.query.nominationPools.poolMembers should yield details about pool members.

The result should be a Map so we should be able to iterate the .entries / .keys.

(async () {
  const provider = new WsProvider('wss://kusama-rpc.polkadot.io')
  const api = await ApiPromise.create({ provider: provider })

  var addresses = [
    'F3opxRbN5ZavB4LTn2JaUnScQc7G7G177CPnqjBpa9F9Gdr', // pool 50 stash
    'F3opxRbN5ZavB4LTn2aKWL2iuHJifMsqn8uLnR2HQ1yQs7t', // pool 50 reward
    'HhYuQCR1pJKVwPruCSNr8xp4R1ovqtAbNy3S8VuMXsPtBmH', // pool 50 depositor/root/etc
  ]

  addresses.forEach(async (address) => {
    console.log('address', address)
    var members = await api.query.nominationPools.poolMembers.entries(address)
    var keys    = await api.query.nominationPools.poolMembers.keys(address)
    
    console.log('members', members, 'keys', keys)
    // const accountIds = keys.map(({ args: [accountId] }) => accountId)
    const accountIds = keys.map(({ args }) => args)
    console.debug('accountIds', accountIds)

    members.forEach(([key, member]) => {
      console.log('key arguments:', key.args.map((k) => k.toHuman()));
      console.log('     exposure:', member.toHuman());
    })
  })
})()

However, I can't get anything from the entries() or keys()

returns

address F3opxRbN5ZavB4LTn2JaUnScQc7G7G177CPnqjBpa9F9Gdr
address F3opxRbN5ZavB4LTn2aKWL2iuHJifMsqn8uLnR2HQ1yQs7t
address HhYuQCR1pJKVwPruCSNr8xp4R1ovqtAbNy3S8VuMXsPtBmH
done...
members [] keys []
accountIds []
members [] keys []
accountIds []
members [] keys []
accountIds []

Just calling await api.query.nominationPools.poolMembers(POOL_ADDRESS) produces:

    {
        "poolId" : 34,
        "points" : 1011793913984.0,
        "rewardPoolTotalEarnings" : 449109804460.0,
        "unbondingEras" : {}
    },

Answer 1

It is a map. So to get .entries() you specify no parameters as per the docs. Params would only come into play with higher-order maps as per docs.

To get all the entries of the pools -

const e = await api.query.nominationPools.poolMembers.entries()

e.forEach(([k, v]) =>
  console.log(
    /* AccountId */
    k.args[0].toString(),
    /* Pool info */
    JSON.stringify(v.toHuman())
  )
)

Which would look like something like the following on Kusama -

GyBph4GJZsiMNJv53mACcujkWcm8NvWF7o2s2pf6PU1efh1 {"poolId":"46","points":"100,000,000,000","rewardPoolTotalEarnings":"10,378,313,014","unbondingEras":{}}
Fk5Z52gA8Ue5G3jNWtvJzNARU1HK12ufsa5xZuDgKvQK5KX {"poolId":"43","points":"1,000,000,000,000","rewardPoolTotalEarnings":"91,827,296,941","unbondingEras":{}}
GUiPpM5wF4KhEiTt2emUYB9VpBSuyEPYhRsE15Ur75Q4ToM {"poolId":"54","points":"5,000,000,000,000","rewardPoolTotalEarnings":"1,713,575,059","unbondingEras":{}}
EFQ1wXD4X1KvV68Ks9VsM2XEjrGZhZo14sjSLQndCTgTRrU {"poolId":"2","points":"2,138,360,777,446","rewardPoolTotalEarnings":"9,324,915,743,936","unbondingEras":{}}
G5NLBLGAUgozcXseaWSsCpfXnxqHcSW7nAAZ689PvspThnE {"poolId":"34","points":"500,000,000,000","rewardPoolTotalEarnings":"562,215,251,310","unbondingEras":{}}
DE1QQkVPp8XVksN4v6qnQYWUjMBBrPGLkHtHM4zZ8N9Vmoc {"poolId":"5","points":"1,000,000,000,000","rewardPoolTotalEarnings":"0","unbondingEras":{}}
FaJi8E1WkeGDR7f79SyburcAkzh78X587diwWhKezDxn1p8 {"poolId":"1","points":"35,000,000,000,000","rewardPoolTotalEarnings":"300,374,601,212","unbondingEras":{}}
JKYYceWYMAoJMEw9CJWMxmfA7fZbc3he9JKDt7ivYvKXmkq {"poolId":"7","points":"6,000,000,000,000","rewardPoolTotalEarnings":"0","unbondingEras":{}}
...