how to transform the data from one schema to other schema?

Question

i am trying to convert the given data into other format but couldn't do it.

input:

const arr= [{acc:"12345",address:{state:"tx",zip:"9999"}},
            {acc:"54321",address:{state:"tx",zip:"9999"}},
            {acc:"67891",address:{state:"ca",zip:"8888"}},
            {acc:"19876",address:{state:"ca",zip:"8888"}}]

expected o/p:

[
  {
  address: '{state:"tx",zip:"9999"}',
  accounts: ["12345","54321"]
   },
  {
  address: '{state:"ca",zip:"8888"}',
  accounts: ["67891","19876"]
   },

]

this is what i have tried

const arr= [{acc:"12345",address:{state:"tx",zip:"9999"}},
            {acc:"54321",address:{state:"tx",zip:"9999"}},
            {acc:"67891",address:{state:"ca",zip:"8888"}},
            {acc:"19876",address:{state:"ca",zip:"8888"}}]

let res = {}

arr.forEach(item=>{
  const formattedAddress = JSON.stringify(item.address) ;
  if(!res[formattedAddress]){
  res[formattedAddress] = []
  }
})

for(let i in res){
  arr.forEach(item=>{
    const formattedAddress = JSON.stringify(item.address);
    if(formattedAddress === i){
      res[i].push(item.acc)
    }
  })
}

console.log(res)

Answer 1

Group into an object or Map indexed by <state>_<zip>, then take the values of the object.

const arr= [{acc:"12345",address:{state:"tx",zip:"9999"}},
            {acc:"54321",address:{state:"tx",zip:"9999"}},
            {acc:"67891",address:{state:"ca",zip:"8888"}},
            {acc:"19876",address:{state:"ca",zip:"8888"}}]

const groupedByAddress = {};
for (const { acc, address } of arr) {
  const key = address.state + '_' + address.zip;
  groupedByAddress[key] ??= { address, accounts: [] };
  groupedByAddress[key].accounts.push(acc);
}
console.log(Object.values(groupedByAddress));

Answer 2

You could use a map with the stringified address as the key and an array as the accounts:

const arr = [{ acc: "12345", address: { state: "tx", zip: "9999" } },
{ acc: "54321", address: { state: "tx", zip: "9999" } },
{ acc: "67891", address: { state: "ca", zip: "8888" } },
{ acc: "19876", address: { state: "ca", zip: "8888" } }]

let results = new Map<String, String[]>()

arr.forEach(item => {
    const addressString = JSON.stringify(item.address)

    const entries = results.get(addressString) || []
    entries.push(item.acc)

    results.set(addressString, entries)
})

results.forEach((val, key) => {
    console.log({
        address: key,
        accounts: val
    })
})