Question 200456 in Javascript Question posted in
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How to filter an array within array of objects in javascript?

I have an array of objects containing information about city and state.
My array of objects look like this:

Sample Input

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

I need to filter based on statecode and citydescription. If I pass state code as TN and city description as Chennai
I need a following output

Sample output

Code: T001

Tried the following and able to filter based on state

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

2

Answers


  1. 0

    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:

    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)
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  2. 0

    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 …

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