Building array from object of arrays returns undefined

Question

So I have this originalArray:

[
  [
    {
       “name”: “Selena”,
       “lastName”: “Gomez”,
       “likes”: {
           “color”: “red”,
           “country”: “Argentina”,
           “state”: {
                “name”: “Buenos Aires”
           }
        },
        “phoneNumber”: “5555555555”,
        “isAvailable”: false
    }
  ],
   [
    {
       “name”: “Nick”,
       “lastName”: “Jonnas”,
       “likes”: {
          “color”: “blue”,
          “country”: “Argentina”,
          “state”: {
            “name”: “Buenos Aires”
          }
        },
        “phoneNumber”: “7777777777”,
        “isAvailable”: true
      },
       {
       “name”: “Joe”,
       “lastName”: “Jonnas”,
       “likes”: {
            “color”: “yellow”,
            “country”: “Argentina”,
            “state”: {
                 “name”: “Buenos Aires”
            }
        },
        “phoneNumber”: “9999999999”,
        “isAvailable”: false
      }
    ]
]

As you can see is an Object that has the form of (2) [Array(1), Array(2)] and I want to iterate over the object and get only the phoneNumbers items.

Expected output:

['55555555555', '7777777777', '9999999999']

I've tried:

const newArray= originalArray.map(element => element.phoneNumber);

But it returns undefined, actually I tried accessing with . like originalArray.phoneNumber and shows undefined too.

I also tried with this approach with no result:

var newArray = originalArray.filter(obj => {
  return obj.phoneNumber != null
})

Is there a way to iterate over the object, look up the phoneNumber key, and add those results to a new array?

originalArray is an Array of Arrays. Arrays do not have a phoneNumber property. I don’t know why you expected this filter to work. Arrays don’t have a value property either; none of your objects do. Have you considered flattening the array first? — Sebastian Simon
– Sebastian Simon, Commented Feb 5, 2022 at 20:14
So why if I do typeof(originalArray) it returns 'object'? — Danny
– Danny, Commented Feb 5, 2022 at 20:19
Arrays are a special type of object and `typeof [] == 'object'`` — charlietfl
– charlietfl, Commented Feb 5, 2022 at 20:21
@Danny Have you read the documentation? See Why does typeof array with objects return "object" and not "array"?. — Sebastian Simon
– Sebastian Simon, Commented Feb 5, 2022 at 20:21

max ivaneychyk · Accepted Answer · 2022-02-05 20:20:32Z

1

const phoneNumbers = originalArray.flat().map(element => element.phoneNumber);

answered Feb 5, 2022 at 20:20

max ivaneychyk

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Comments

Yimin · Accepted Answer · 2022-02-05 20:35:43Z

const originalArray = [
  [
    {
      name: "Selena",
      lastName: "Gomez",
      likes: {
        color: "red",
        country: "Argentina",
        state: {
          name: "Buenos Aires",
        },
      },
      phoneNumber: "5555555555",
      isAvailable: false,
    },
  ],
  [
    {
      name: "Nick",
      lastName: "Jonnas",
      likes: {
        color: "blue",
        country: "Argentina",
        state: {
          name: "Buenos Aires",
        },
      },
      phoneNumber: "7777777777",
      isAvailable: true,
    },
    {
      name: "Joe",
      lastName: "Jonnas",
      likes: {
        color: "yellow",
        country: "Argentina",
        state: {
          name: "Buenos Aires",
        },
      },
      phoneNumber: "9999999999",
      isAvailable: false,
    },
  ],
];

const phoneNums = originalArray.flat().map((element) => element.phoneNumber);

console.log(phoneNums);

Serge · Accepted Answer · 2022-02-05 20:54:58Z

1

You were close, just needed to add map. Try this

var newArray = originalArray.flat()
.filter(obj => obj.phoneNumber!=null)
.map(obj => { return obj.phoneNumber;});

edited Feb 5, 2022 at 20:54

answered Feb 5, 2022 at 20:47

Serge

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Comments

Rohìt Jíndal · Accepted Answer · 2022-02-07 13:35:07Z

We can achieve this by :

Flattening the multidimensional array into single array.
looping through each object using Array.map() to fetch the phone number.
This step is for safe side to eliminate the empty or null phone numbers using Array.filter()

Working Demo :

let originalArray = [
  [
    {
       "name": "Selena",
       "lastName": "Gomez",
       "likes": {
           "color": "red",
           "country": "Argentina",
           "state": {
                "name": "Buenos Aires"
           }
        },
        "phoneNumber": "5555555555",
        "isAvailable": false
    }
  ],
   [
    {
       "name": "Nick",
       "lastName": "Jonnas",
       "likes": {
          "color": "blue",
          "country": "Argentina",
          "state": {
            "name": "Buenos Aires"
          }
        },
        "phoneNumber": "7777777777",
        "isAvailable": true
      },
       {
       "name": "Joe",
       "lastName": "Jonnas",
       "likes": {
            "color": "yellow",
            "country": "Argentina",
            "state": {
                 "name": "Buenos Aires"
            }
        },
        "phoneNumber": "9999999999",
        "isAvailable": false
      }
    ]
];

const flatArray = originalArray.flat().map((obj) => obj.phoneNumber).filter((item) => item);

console.log(flatArray);

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