Convert JSOn object into a flat JSON Array

Question

I have a nested JSON object that getting from a mongoDB query that i would like to convert into flat JSON array .I am using nested mondo documents, but i would like to show the data in a more readble way. My JSON has the following structure:

{
 "country": "Country A",
 "_id": "1"
 "regions": [{
        "region": "region A1",
        "cities": [{
                "city": "city A11"
            },
            {
             "city": "city A12"
            }
        ]
        },
        {
            "region": "region A2",
            "cities": [{
                    "city": "city A21"
                },
                {
                    "city": "city A22"
                }
            ]
        }
    ]
}

I want to show only the important information and not the structure of the nested array. How i can modify my data in Javascript on order to achieve the following result.

[{
"country": "Country A",
"region":"Region A1",
"city": "City A11"
},
 {
"country": "Country A",
"region":"Region A1",
"city": "City A12"
},

-------------

{
"country": "Country A",
"region":"Region A2",
"city": "City A22"
}]

I have tried to do in this way but it´s not working.

exports.get_places = (req, res, next) => {
Place.findOne({_id:req.params.id})
    .then(data => {
      let flat = arr.reduce((arr, {country, regions}) => {
          regions.forEach(({region, cities}) => {
          cities.forEach(({city}) => {
       arr.push({country, region, city})
    })
})
return arr
}, [])
console.log(flat)
    })
    .catch(error => {
        return next(error);
    });
}

The posted question does not appear to include any attempt at all to solve the problem. StackOverflow expects you to try to solve your own problem first, as your attempts help us to better understand what you want. Please edit the question to show what you've tried, so as to illustrate a specific roadblock you're running into a minimal reproducible example. For more information, please see How to Ask and take the tour. — CertainPerformance
– CertainPerformance, Commented Dec 10, 2018 at 20:40

ic3b3rg · Accepted Answer · 2018-12-10 21:22:07Z

1

I believe this will perform the transformation you seek:

const country = {
  "country": "Country A",
  "_id": "1",
  "regions": [
    {
      "region": "region A1",
      "cities": [
        {
          "city": "city A11"
        },
        {
          "city": "city A12"
        }
      ]
    },
    {
      "region": "region A2",
      "cities": [
        {
          "city": "city A21"
        },
        {
          "city": "city A22"
        }
      ]
    }
  ]
};

const flat = country.regions.flatMap(({region, cities}) =>
  cities.map(({city}) => ({country: country.country, region, city})
));

console.log(flat);

answered Dec 10, 2018 at 21:22

ic3b3rg

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Comments

Marcos · Accepted Answer · 2018-12-10 20:55:39Z

0

I think you need use map function, and transfomr every object in nested arrays as the object you want to obtain. If I undesrstand you good you will need somthing like this:

let desiredArray = country.region.map(x => {
    country:x.country,
    region:x.region,
    cities:x.city
})

its little confuse to undestand what you really want but I think you can start to work with that

answered Dec 10, 2018 at 20:55

Marcos

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Comments

mster · Accepted Answer · 2020-08-16 08:32:07Z

0

As is the typical case for Node... there's a package for that! A popular one is called flat (zero deps!!). https://www.npmjs.com/package/flat

From their README:

var flatten = require('flat')
 
flatten({
    key1: {
        keyA: 'valueI'
    },
    key2: {
        keyB: 'valueII'
    },
    key3: { a: { b: { c: 2 } } }
})
 
// {
//   'key1.keyA': 'valueI',
//   'key2.keyB': 'valueII',
//   'key3.a.b.c': 2
// }

You can also implement your own! :)

If you need some hints, I've implemented one in a recent project of mine except it returns an array.

Check it out: https://github.com/mster/fireferret/blob/e99b6e8f23d4a0783c8a0706cd163093936d6c69/lib/utils/flatmapper.js#L6-L50

answered Aug 16, 2020 at 8:32

mster

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