Convert nested JSON array into flat JSON array

Question

I have a nested JSON array that getting from a mongoDB query that i would like to convert into flat JSON .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",
     "regions": [{
            "region": "region A1",
            "cities": [{
                    "city": "city A11"
                },
                {
                 "city": "city A12"
                }
            ]
            },
            {
                "region": "region A2",
                "cities": [{
                        "city": "city A21"
                    },
                    {
                        "city": "city A22"
                    }
                ]
            }
        ]
    },
    {
        "country": "Country B",
        "regions": [{
                "region": "region B1",
                "cities": [{
                        "city": "city B11"
                    },
                    {
                        "city": "city B12"
                    }
                ]
            },
            {
                "region": "region B2",
                "cities": [{
                        "city": "city B21"
                    },
                    {
                        "city": "city B22"
                    }
                ]
            }
        ]
    }
]

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 B",
    "region":"Region B1",
    "city": "City B11"
  },
  -----------
   {
    "country": "Country B",
    "region":"Region B2",
    "city": "City B22"
  }
]

What is the simpliest way to acheive this result?

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– CertainPerformance, Commented Dec 5, 2018 at 1:13

Mark · Accepted Answer · 2018-12-05 01:21:13Z

1

The simplest way is to just loop through and create an array. You can do this with reduce():

let arr = [{"country": "Country A","regions": [{"region": "region A1","cities": [{"city": "city A11"},{"city": "city A12"}]},{"region": "region A2","cities": [{"city": "city A21"},{"city": "city A22"}]}]},{"country": "Country B","regions": [{"region": "region B1","cities": [{"city": "city B11"},{"city": "city B12"}]},{"region": "region B2","cities": [{"city": "city B21"},{"city": "city B22"}]}]}]

let flat = arr.reduce((arr, {country, regions}) => {
    regions.forEach(({region, cities}) => {
        cities.forEach(({city}) => {
            arr.push({country, region, city})
        })
    })
    return arr
}, [])
console.log(flat)

answered Dec 5, 2018 at 1:21

Mark

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