The process of extracting all arrays from a JSON object

Within my JSON object, there is a list of countries each with multiple regions stored in an array. My goal is to extract and combine all the regions into one single list. However, when I attempt to map the data, it does not consolidate all the regions as expected. What might be causing this issue?

Below is the code snippet used to retrieve the JSON data specifically focusing on extracting the regions:

this.service.getData().subscribe((data: any) => {
      this.list = data.map((c:any) => c.Regions);
    });

The structure of the JSON object looks like this:

{

    "Country": "Antarctica",
    "Regions": [
        "Adélie Land",
        "Argentine Antarctica",
        "Australian Antarctic Territory",
        "British Antarctic Territory",
        "Chilean Antarctic Territory",
        "Peter I Island",
        "Queen Maud Land",
        "Ross Dependency"
    ]
},
{
    "Country": "Antigua And Barbuda",
    "Regions": []
},
{
    "Country": "Argentina",
    "Regions": [
        "Buenos Aires",
        "Cordoba",
        "Buenos Aires City",
        "Catamarca",
        "Chaco",
        "Chubut",
        "San Luis",
        "Santa Cruz",
        "Santa Fe",
        "Santiago del Estero",
        "Tierra del Fuego",
        "Tucuman",
        "Mendoza",
        "Misiones",
        "Neuquen",
        "Rio Negro",
        "Salta",
        "San Juan",
        "Corrientes",
        "Entre Rios",
        "Formosa",
        "Jujuy",
        "La Pampa",
        "La Rioja"
    ]
},

Answer №1

utilize the flatMap method

here's an example of how to do it

const extract = data => data.flatMap(d => d.Regions)

const data = [{

    "Country": "Antarctica",
    "Regions": [
        "Adélie Land",
        "Argentine Antarctica",
        "Australian Antarctic Territory",
        "British Antarctic Territory",
        "Chilean Antarctic Territory",
        "Peter I Island",
        "Queen Maud Land",
        "Ross Dependency"
    ]
},
{
    "Country": "Antigua And Barbuda",
    "Regions": []
},
{
    "Country": "Argentina",
    "Regions": [
        "Buenos Aires",
        "Cordoba",
        "Buenos Aires City",
        "Catamarca",
        "Chaco",
        "Chubut",
        "San Luis",
        "Santa Cruz",
        "Santa Fe",
        "Santiago del Estero",
        "Tierra del Fuego",
        "Tucuman",
        "Mendoza",
        "Misiones",
        "Neuquen",
        "Rio Negro",
        "Salta",
        "San Juan",
        "Corrientes",
        "Entre Rios",
        "Formosa",
        "Jujuy",
        "La Pampa",
        "La Rioja"
    ]
}]

console.log(extract(data))

Answer №2

Below is a demonstration of how the code interacts with the provided data:

const regionsList = []
Object.keys(data).map(key => {
  if (key === "Regions") regionsList.push(...data[key])
}); 

console.log(regionsList);
<script>
const data = {
    "Country": "Antarctica",
    "Regions": [
        "Adélie Land",
        "Argentine Antarctica",
        "Australian Antarctic Territory",
        "British Antarctic Territory",
        "Chilean Antarctic Territory",
        "Peter I Island",
        "Queen Maud Land",
        "Ross Dependency"
    ]
}
</script>

Answer №3

Your information is structured as an object, not an array. To access the regions, you may need to iterate over the keys and retrieve the relevant data. Here's a potential approach for accessing the regions within your data object:

this.service.getData().subscribe((data: any) => {
   this.list = Object.keys(data).flatMap((key) => data[key].Regions);
});

Consider using flatMap from lodash for a cleaner implementation.

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