Pick JSON array object by its key

Question

I have JSON array that looks like

var data = {
  "fields": [{
      "firstName": {
        "fieldName": "First Name",
        "required": true,
        "provided": false
      }
    },
    {
      "lastName": {
        "fieldName": "Last Name",
        "required": true,
        "provided": false
      }
    },
    {
      "email": {
        "fieldName": "Email",
        "required": true,
        "provided": false
      }
    }
  ]
}

Further down I am trying to do this:

Access the fieldName of the firstName object. Is there to do that without using the index?

data.fields gives me the array of object. From there onwards, I do not seem to be able to access with the object key.

Also, data.fields[0] gives the whole firstName object but I can't seem to do data.fields[0]["field"] or data.fields[0].field

Thanks.

data.fields gives me the array of object. From there onwards, I do not seem to be able to access with the object key. - data.fields[0].firstName.fieldName — VLAZ
– VLAZ, Commented May 18, 2018 at 0:08
just a heads up ... there is no JSON in your question at all — Jaromanda X
– Jaromanda X, Commented May 18, 2018 at 0:15

CertainPerformance · Accepted Answer · 2018-05-18 00:16:03Z

You can use .find to find a particular element in an array:

var data={"fields":[{"firstName":{"fieldName":"First Name","required":!0,"provided":!1}},{"lastName":{"fieldName":"Last Name","required":!0,"provided":!1}},{"email":{"fieldName":"Email","required":!0,"provided":!1}}]}
const firstNameFieldName = data.fields
  .find(obj => 'firstName' in obj)
  .firstName.fieldName;
console.log(firstNameFieldName);

Also note that you do not have a "JSON array". JSON is a notation for representing objects as strings. You just have a plain object.

You might find it easier if you turned the fields into an object instead of an array, such as:

var data = {
  fields: {
    "firstName": {
      "fieldName": "First Name",
      "required": true,
      "provided": false
    },
    "lastName": {
      "fieldName": "Last Name",
      "required": true,
      "provided": false
    },
    "email": {
      "fieldName": "Email",
      "required": true,
      "provided": false
    }
  }
};

Then you could access the properties directly with, for example, data.fields.firstName without having to resort to .find.

Zohaib Ijaz · Accepted Answer · 2018-05-18 00:11:09Z

1

data.fields[0] is this object

{
    "firstName": {
        "fieldName": "First Name",
        "required": true,
        "provided": false
    }
}

So if you want to access anything indide that object which is firstName key, you don't need to use index because it is an Object and not an Array. You can access it like data.fields[0].firstName which will be equal to

{
    "fieldName": "First Name",
    "required": true,
    "provided": false
}

And further if you want to access inner fields/properties, do data.fields[0].firstName.fieldName and so on

answered May 18, 2018 at 0:11

Zohaib Ijaz

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