How to return keys that have empty values from an array of objects as a string in JavaScript?

Question

I have an array of objects where some keys return an empty value. When an empty value appears I'd like to return that key as a string.

For example this array:

'products': [{                           
        'name': 'Test product',     
        'id': '',
        'price': '',
        'brand': 'AwesomeBrand',
        'colour': 'Gray',
        'quantity': 1
       },
       {
        'name': '',
        'id': '123',
        'price': '',
        'brand': 'AwesomeBrand',
        'colour': 'Black',
        'quantity': 1
       }]

In the example above I want to return the following:

'id, price, name'

I've tried the following that kind of does the job. However, it still returns as an array. Then I JSON.strigify it but that returns an ugly string. I tried replacing/RegEx cleaning it however, the program I'm using uses a Sandboxed Version of JavaScript so some features are not accessible.

I'm struggling to grasp the concept of accessing keys and values in an array of objects. So that is part of my problem.

var productArray = ecomValues || [];
var emptyArray = [];

var output = productArray.reduce(function (previousValue, currentValue, currentIndex) {
  var keys = Object.keys(currentValue).filter(function (key) {
    return !currentValue[key];/  });

  if (keys.length) {
    previousValue[currentIndex] = keys;
  }

  return previousValue;
}, {});

var emptyValues = output;
emptyArray.push(emptyValues);

Anyone that can help me with my issue?

Do you want the string for each object in the array? Or all the keys combined? — 0stone0, Apr 08 '22 at 09:10
All keys combined. So I prefer to have it return a single string with 'id, name' etc. Preferably comma separated. but you can use the .join for that — Jorginton, Apr 08 '22 at 09:24
@Jorginton I added an answer. Please have a look. Hope that will work as per your expectation — Debug Diva, Apr 09 '22 at 06:59
Hey Rohit! Thank you! That sadly does not work since I can't use the Set method. — Jorginton, Apr 12 '22 at 14:31

Nina Scholz · Answer 1 · 2022-04-08T10:11:51.107

0

You could iterate the array and get the keys and add the keys if a falsy value is found.

const
    products = [{ name: 'Test product', id: '', price: '', brand: 'AwesomeBrand', colour: 'Gray', quantity: 1 }, { name: '', id: '123', price: '', brand: 'AwesomeBrand', colour: 'Black', quantity: 1 }],
    empty = Array.from(products.reduce((s, o) => {
        Object.keys(o).forEach(k => {
            if (o[k] === '') s.add(k);
        });
        return s;
    }, new Set));

console.log(empty.join(', '));

A solution without Set.

const
    products = [{ name: 'Test product', id: '', price: '', brand: 'AwesomeBrand', colour: 'Gray', quantity: 1 }, { name: '', id: '123', price: '', brand: 'AwesomeBrand', colour: 'Black', quantity: 1 }],
    empty = Array.from(products.reduce((r, o) => {
        Object.keys(o).forEach(k => {
            if (o[k] === '' && !r.includes(k)) r.push(k);
        });
        return r;
    }, []));

console.log(empty.join(', '));

edited Apr 08 '22 at 10:11

answered Apr 08 '22 at 09:11

Nina Scholz

376,160
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Thank you for your reply! I do get an error when I try to use the Set method: 1 Error(s) parsing the input: extraneous input 'Set' expecting {')', ','} Offending token '' at 15,7. – Jorginton Apr 08 '22 at 09:31
does it work above? – Nina Scholz Apr 08 '22 at 09:32
The snippet works! However, when I copy and paste it it says that it can't read the 'Set)' bit. Is there a way around the Set method? – Jorginton Apr 08 '22 at 09:54

score 0 · Answer 2 · answered Apr 08 '22 at 09:11

0

We can use reduce() to create an array with all the keys that are empty

To find the empty keys we can use this for an example
Then, we remove all duplicate keys
And join() the array to a string

const data = {'products': [{'name': 'Test product', 'id': '', 'price': '', 'brand': 'AwesomeBrand', 'colour': 'Gray', 'quantity': 1 }, {'name': '', 'id': '123', 'price': '', 'brand': 'AwesomeBrand', 'colour': 'Black', 'quantity': 1 }]};

const emptyKeys = data.products.reduce((prev, cur) => 
    [ ...prev, ...Object.keys(cur).filter((key) => !cur[key]) ], [])
    .filter((v, i, a) => a.indexOf(v) === i)
    .join(', ');

console.log(emptyKeys);

id, price, name

answered Apr 08 '22 at 09:11

0stone0

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I do get an array when I execute it. I think the Sandboxed JS can't read the ... 1 Error(s) parsing the input: mismatched input '.' expecting {'~', 'function', 'null', 'typeof', 'undefined', 'getContainerVariable', String, Number, Boolean, '++', '--', '-', '!', Identifier, ']', '{', '[', '('} Offending token '.' at 11,6. – Jorginton Apr 08 '22 at 09:32
Did you run the snippet? Working fine, maybe you can add your code to your question? – 0stone0 Apr 08 '22 at 09:38
The snippet works but the program can't read the dots (...). Is there a way around this? – Jorginton Apr 08 '22 at 09:53
Not sure what you mean by that. WE'll need to see your code to know what you're talking about. – 0stone0 Apr 08 '22 at 10:09

score 0 · Answer 3 · answered Apr 08 '22 at 09:51

Iterate products with Array.flatMap(), filter out all keys with non-empty values, and then make the array unique by using a Set, and spreading back to an array:

const products = [{ name: 'Test product', id: '', price: '', brand: 'AwesomeBrand', colour: 'Gray', quantity: 1 }, { name: '', id: '123', price: '', brand: 'AwesomeBrand', colour: 'Black', quantity: 1 }]

const result = [...new Set(products.flatMap(
  obj => Object.keys(obj)
    .filter(key => obj[key] === '')
))]

console.log(result);

score 0 · Answer 4 · answered Apr 08 '22 at 12:14

You can simply achieve that by iterating the array using Array.forEach() along with Object.keys() method.

Demo :

const products = [{                           
  'name': 'Test product',     
  'id': '',
  'price': '',
  'brand': 'AwesomeBrand',
  'colour': 'Gray',
  'quantity': 1
}, {
  'name': '',
  'id': '123',
  'price': '',
  'brand': 'AwesomeBrand',
  'colour': 'Black',
  'quantity': 1
}];

const res = [];

products.forEach((obj) => {
    Object.keys(obj).forEach((objKey) => {
    !obj[objKey] ? res.push(objKey) : ''
  })
})

// Remove duplicate elements from an array
console.log([...new Set(res)]);

How to return keys that have empty values from an array of objects as a string in JavaScript?

4 Answers4