Loop Through Complicated JSON Object with Angular 6

Question

I have a JSON object that I'm only interested in one of the key "codes" and its values. I would like to run a loop to get those values for every region and country and city and store them in an array.

{
"region":{
    "America":{
        "countries":{
            "US":{
                "cities":{
                    "NY":{
                        "codes":["142","2243","312","4123","5132"]
                    },
                    "LA":{
                        "codes":["1465","2465","3453","4132","542"]
                    }
                }
            },
            "CANADA":{
                "cities":{
                    "TORNTO":{
                        "codes":["1465","2465","3453","4132","542"]
                    }
                }

            }
        }
    },
    "ASIA":{
        "countries":{
            "India":{
                "cities":{
                    "Delhi ":{
                        "codes":["142","2243","312","4123","5132"]
                    },
                    "Calcutta":{
                        "codes":["1465","2465","3453","4132","542"]
                    }
                }
            },
            "CHINA":{
                "cities":{
                    "HONKKON":{
                        "codes":["1465","2465","3453","4132","542"]
                    }
                }

            }
        }
    }

}

}

what I have done

getCodes(regions){
let ccode = [];
for (let key of Object.values(region)) {
    for (let temp of Object.values(key)) {
        for (let ctemp of Object.values(temp)) {
            for (btemp of Object.values(ctemp)) {
                for (let bbtemp of Object.values(btemp)) {
                    ccode.push(...bbtemp["code"])
}
            }
        }
    }

}

}

However, all my interest is to collect the codes values in every single region and put them together in a list. any practical way?

Amr Salama · Accepted Answer · 2020-02-07 21:44:50Z

2

You can go with a recursive approach like this:

const extractCodes = obj => {
  let codes = [];
  for (const key in obj) {
    if (key === 'codes') return [...obj[key]];
    else {
      codes = [...codes, ...extractCodes(obj[key])];
    }
  }
  return codes;
};

const region = {
  America: {
    countries: {
      US: {
        cities: {
          NY: {
            codes: ['142', '2243', '312', '4123', '5132']
          },
          LA: {
            codes: ['1465', '2465', '3453', '4132', '542']
          }
        }
      },
      CANADA: {
        cities: {
          TORNTO: {
            codes: ['1465', '2465', '3453', '4132', '542']
          }
        }
      }
    }
  },
  ASIA: {
    countries: {
      India: {
        cities: {
          'Delhi ': {
            codes: ['142', '2243', '312', '4123', '5132']
          },
          Calcutta: {
            codes: ['1465', '2465', '3453', '4132', '542']
          }
        }
      },
      CHINA: {
        cities: {
          HONKKON: {
            codes: ['1465', '2465', '3453', '4132', '542']
          }
        }
      }
    }
  }
};

console.log(extractCodes(region));

In case you want to extract unique values only (codes without repetition), You can use Set:

const extractCodes = obj => {
  let codes = [];
  for (const key in obj) {
    if (key === 'codes') return [...obj[key]];
    else {
      codes = [...new Set([...codes, ...extractCodes(obj[key])])];
    }
  }
  return codes;
};

const region = {
  America: {
    countries: {
      US: {
        cities: {
          NY: {
            codes: ['142', '2243', '312', '4123', '5132']
          },
          LA: {
            codes: ['1465', '2465', '3453', '4132', '542']
          }
        }
      },
      CANADA: {
        cities: {
          TORNTO: {
            codes: ['1465', '2465', '3453', '4132', '542']
          }
        }
      }
    }
  },
  ASIA: {
    countries: {
      India: {
        cities: {
          'Delhi ': {
            codes: ['142', '2243', '312', '4123', '5132']
          },
          Calcutta: {
            codes: ['1465', '2465', '3453', '4132', '542']
          }
        }
      },
      CHINA: {
        cities: {
          HONKKON: {
            codes: ['1465', '2465', '3453', '4132', '542']
          }
        }
      }
    }
  }
};

console.log(extractCodes(region));

edited Feb 7, 2020 at 21:44

answered Feb 7, 2020 at 21:29

Amr Salama

1,0001 gold badge7 silver badges21 bronze badges

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8 Comments

Anmar Al Shammari Over a year ago

I'm trying to implement the method, but it is not taking the const const extractCodes = obj => { let codes = []; for (const key in obj) { if (key === 'codes') return [...obj[key]]; else { codes = [...new Set([...codes, ...extractCodes(obj[key])])]; } } return codes; }; is this a type script? if yes, where should implement this?

Amr Salama Over a year ago

It's javascript, which could be used as typescript as well. You can use it as part of controller, or service or even in utils file. it depends on project structure.

Anmar Al Shammari Over a year ago

Can you reform it in the same format I did to obe readable? @amr salama

Anmar Al Shammari Over a year ago

it says "a class member can not have the const keyword. extractCoodes has a red underlined.

Amr Salama Over a year ago

just update const extractCodes = obj => { to extractCodes (obj) {

|

Đinh Carabus · Accepted Answer · 2020-02-07 21:56:13Z

0

This is kind of an oldschool approach, but it will work in every browser:

var json = { ... };

function getCodes(obj) {
  var codes = [];
  for (var p in obj) {
    if (obj.hasOwnProperty(p)) {
      if (p === "codes") {
        codes = codes.concat(obj[p]);
      } else if (typeof obj[p] === "object") {
        codes = codes.concat(getCodes(obj[p]));
      }
    }
  }
  return codes;
}

var codes = getCodes(json); // ["142", "2243", "312", "4123", ...]

edited Feb 7, 2020 at 21:56

answered Feb 7, 2020 at 21:30

Đinh Carabus

3,5054 gold badges26 silver badges47 bronze badges

1 Comment

Anmar Al Shammari Over a year ago

it is not taking this in the typescript file. it is saying syntax is not readable for function.

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