Dynamic object keys to array

Question

I have an array of objects with dynamic country keys. I need to get the country key and put it into a new array. The array can contain more dynamic keys with the name of the countries.

const arr1 = [
  {
    id: 1,
    label: 'CA',
    value: 9,
    Canada: 9,
  },
  {
    id: 2,
    label: 'US',
    value: 7,
    'United States': 7,
  },
  {
    id: 3,
    label: 'AU',
    value: 5,
    Australia: 5,
  },
];

const result = ['Canada', United States', 'Australia']

Do you have control over the code that creates that array? Objects with variable keys like that are inconvenient at best, and plainly horrible to deal with in general... Ideally, you'd change how that array is created in the first place. — Cerbrus
– Cerbrus, Commented Sep 27, 2021 at 10:42
@Cerbrus, I'll transform the resulting array. I use the Nivo Bar library and it has prop keys - an array of strings ['value'] for displaying a value for the label. I cannot use {name: country}. — IncognitoUser
– IncognitoUser, Commented Sep 27, 2021 at 11:10

Cerbrus · Accepted Answer · 2021-09-27 10:46:42Z

2

You can use a blacklist to dump all keys you don't want:

const arr1 = [
    { id: 1, label: 'CA', value: 9, Canada: 9 },
    { id: 2, label: 'US', value: 7, 'United States': 7 },
    { id: 3, label: 'AU', value: 5, Australia: 5 },
];

const blacklist = ['id', 'label', 'value'];

const countryNames = arr1.map(row => 
    Object.keys(row)
        .filter(key => !blacklist.includes(key))[0]);

console.log(countryNames)

Object.keys builds an array of keys for that row, then I filter those keys on the blacklist, and return the first remaining entry.

answered Sep 27, 2021 at 10:46

Cerbrus

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Comments

Gynekolog · Accepted Answer · 2021-10-29 08:58:34Z

0

You can use flatMap to prevent getting an undefined value in the result when a key doesn't suit.

const data = [
    { id: 1, label: 'CA', value: 9, Canada: 9, },
    { id: 2, label: 'US', value: 7, 'United States': 7, },
    { id: 3, label: 'AU', value: 5, Australia: 5, },
    { id: 4, },
];

const blacklistedKeys = ['id', 'label', 'value'];

const result = data.flatMap(item => {
    const keys = Object.keys(item);
    const allowedKey = keys.find(key => !blacklistedKeys.includes(key));
    return allowedKey ? [allowedKey] : [];
});

console.log(result);

edited Oct 29, 2021 at 8:58

answered Sep 27, 2021 at 10:52

Gynekolog

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Comments

Hissvard · Accepted Answer · 2021-09-27 10:51:18Z

-1

A blacklist will break if you add more properties.

Have you considered filtering the ones whose first letter is uppercase?

const countryNames = arr1.map(row => 
    Object.keys(row)
        .filter(key => key[0] === key[0].toUpperCase())[0]);

answered Sep 27, 2021 at 10:51

Hissvard

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