Recursive array of property values in array of objects

Question

What I need is an array of property values, recursively collected from an array of objects, this is what I mean:

const regions = [{
  name: 'Europe',
  subRegions: [{
    name: 'BeNeLux',
    territories: [{
      code: 'NL',
      name: 'Netherlands'
    }, {
      code: 'DE',
      name: 'Germany'
    }, {
      code: 'LU',
      name: 'Luxembourgh'
    }]
  }],
  territories: [{
    code: 'UK',
    name: 'United Kingdom'
  }, {
    code: 'AL',
    name: 'Albania'
  }, {
    code: 'ZW',
    name: 'Switzerland'
  }]
}]

I want to get an array of all the country codes in the regions array.

So like:

const expectedOutput = ['NL', 'DE', 'LU', 'AL', 'ZW', 'UK'];

This what I have tried, which partly works but it's not collecting it correctly (I'm also very curious for exploring different / functional setups to solve this problem)

const getAllTerritoryCodesFromRegions = regions => {
  return regions
    .reduce(function r (output, region) {
      if (region?.subRegions?.length) {
        output.subRegions = region.subRegions.reduce(r, output)
      }

      if (region?.territories?.length) {
        output = [
          ...output,
          ...region.territories.map(t => t.code)
        ]
      }

      return output
    }, [])
}

The upper array has the country codes as the code property, the lower array has some country codes in the name property? Is that a typo? — CertainPerformance
– CertainPerformance, Commented Aug 3, 2019 at 21:03

Nina Scholz · Accepted Answer · 2019-08-03 21:05:11Z

3

You could reduce the array by looking for arrays and return the codes.

function getCodes(array) {
    return array.reduce((r, o) => {
        if ('code' in o) {
            r.push(o.code);
            return r;
        }
        Object.values(o).forEach(v => {
            if (Array.isArray(v)) r.push(...getCodes(v));
        });
        return r;
    }, []);
}

const
    regions = [{ name: 'Europe', subRegions: [{ name: 'BeNeLux', territories: [{ code: 'NL', name: 'Netherlands' }, { code: 'DE', name: 'Germany' }, { code: 'LU', name: 'Luxembourgh' }] }], territories: [{ name: 'United Kingdom', code: 'UK' }, { name: 'AL', code: 'Albania' }, { name: 'ZW', code: 'Switzerland' }] }],
    codes = getCodes(regions);

console.log(codes);

answered Aug 3, 2019 at 21:05

Nina Scholz

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Comments

CertainPerformance · Accepted Answer · 2019-08-03 21:04:34Z

Assuming that the code properties should always contain the country codes:

It would probably be easier to create one array on the first call, which gets recursively passed down as a parameter, than to create an array for every call and try to combine it later. Then you just need to forEach over the regions and territories and push the code to that array:

const regions = [{
  name: 'Europe',
  subRegions: [{
    name: 'BeNeLux',
    territories: [{
      code: 'NL',
      name: 'Netherlands'
    }, {
      code: 'DE',
      name: 'Germany'
    }, {
      code: 'LU',
      name: 'Luxembourgh'
    }]
  }],
  territories: [{
    name: 'United Kingdom',
    code: 'UK'
  }, {
    code: 'AL',
    name: 'Albania'
  }, {
    code: 'ZW',
    name: 'Switzerland'
  }]
}];

const getAllTerritoryCodesFromRegions = (regions, allCodes=[]) => {
  regions.forEach(({ territories, subRegions }) => {
    if (territories) {
      territories.forEach(({ code }) => {
        allCodes.push(code);
      });
    }
    if (subRegions) {
      getAllTerritoryCodesFromRegions(subRegions, allCodes);
    }
  });
  return allCodes;
};
console.log(
  getAllTerritoryCodesFromRegions(regions)
);

Morphyish · Accepted Answer · 2019-08-03 21:07:11Z

1

You could do it with a recursive method

const getAllTerritoryCodesFromRegions = array => {
    const output = [];

    array.forEach(item => {
        for (const key in item) {
            if (key === 'code') {
                output.push(item[key]);
            } else if (item.hasOwnProperty(key) && Array.isArray(item[key])) {
                const childOutput = getAllTerritoryCodesFromRegions(item[key]);
                output.push(...childOutput);
            }
        }
    });

    return output;
}

You can find a working example here jsfiddle. However in the dataset from your example you messed up some names and codes.

answered Aug 3, 2019 at 21:07

Morphyish

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