How to filter an array within array of objects in javascript?

I have an array of objects containing information about cities and states. I need to filter based on statecode and citydescription properties.

{
  "stateProvinces": [
    {
      "cities": [
        {
          "code": "T001",
          "citydescription": "Chennai"
        },
        // ...
      ],
      "statecode": "TN"
    },
    // ...
  ]
}

If I pass state code as TN and city description as Chennai I need a following output: Code: T001. Tried the following and able to filter based on state:

const filtervalue = getCityNames.filter((code) => {
  return code.statecode == "TN";
});

A straightforward way is to use 2 find()'s.

First find the matching province, then the matching city.

Of course you can do this in a single command with eg reduce, but I think this is more readable:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const data = {"stateProvinces": [{"cities": [{"code": "T001","citydescription": "Chennai"}, {"code": "T002","citydescription": "Madurai"} ], "statecode": "TN"}, {"cities": [{"code": "E001","citydescription": "Erakulam"}, {"code": "M002","citydescription": "Munnar"} ], "stateCode": "KL"}]}

const findCode = 'TN';
const findCity = 'Chennai';

let res = null;

const foundProvince = data.stateProvinces.find(o => o.statecode === findCode);
if (foundProvince) {
    res = foundProvince.cities.find(c => c.citydescription === findCity)?.code;
}

console.log(res)

<!-- end snippet -->

From my two answering comments on another answer ..

> "for a vast amount of queries on a very large data base I would suggest transforming the data structure once into a map of maps ... thus queries then would look like ... stateCodeAndCityNameBasedCityCodeMap.get('TN')?.get?.('Chennai'); ... or ... stateCodeAndCityNameBasedCityCodeMap.get('KL')?.get?.('Munnar');"

> "Even though a find based iteration exits early the time complexity of a nested find is much higher then a straight linear access on a Map based query path for Map is optimized for fast lookups."

... and in order to prove the above said ...

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const stateProvinces = [{
  cities: [{
    code: "T001", citydescription: "Chennai",
  }, {
    code: "T002", citydescription: "Madurai",
  }],
  statecode: "TN",
}, {
  cities: [{
    code: "E001", citydescription: "Erakulam",
  }, {
    code: "M002", citydescription: "Munnar",
  }],
  statecode: "KL",
}];

const stateCodeAndCityNameBasedCityCodeMap = new Map(
  stateProvinces.map(({ statecode, cities }) => [
    statecode,
    new Map(
      cities.map(({ citydescription, code }) => [ citydescription, code ])
    )
  ])
);
console.log(
  stateCodeAndCityNameBasedCityCodeMap.get('TN')?.get?.('Chennai')
);
console.log(
  stateCodeAndCityNameBasedCityCodeMap.get('KL')?.get?.('Munnar')
);
console.log(
  stateCodeAndCityNameBasedCityCodeMap.get('KL')?.get?.('FOO')
);
console.log(
  stateCodeAndCityNameBasedCityCodeMap.get('BAR')?.get?.('BAZ')
);

<!-- language: lang-css -->

.as-console-wrapper { min-height: 100%!important; top: 0; }

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