Loop through object and check if field is an empty array and return null

Question

I have the following object:

productDetails: {
    cislife: [],
    prime: []
  }

I want to return null instead of empty array if there aren't any values available.

e.g: I want to check if any of the arrays are empty and return null as the key value, either cislife or prime. If prime is populated and cislife is not then i would return the values for prime and null for cislife

Any ideas?

Please precise the problem. Where's the loop? Which array are you talking about - the cislife or prime? — aherok
– aherok, Commented Jul 25, 2019 at 20:24
Okay. I want to check if any of the arrays are empty and return null, either cislife or prime. If prime is populated and cislife is not then i would return the values for prime and null for cislife. — O'Dane Brissett
– O'Dane Brissett, Commented Jul 25, 2019 at 20:26
return... where? You have a function? Could you edit your question, and share our attempt, give the output for several border cases? — trincot
– trincot, Commented Jul 25, 2019 at 20:29

Tom O. · Accepted Answer · 2019-07-25 20:35:55Z

4

You could do something like this where you use Array.prototype.reduce and build out an object literal, replacing [] with null where appropriate:

const productDetails = {
  cislife: [],
  prime: [],
  nonEmptyExample: [1, 2, 3],
  nonArrayExample: 'a string!'
};

const emptyArraysToNulls = o => {
  return Object.entries(productDetails).reduce((accum, entry) => {
    const [key, val] = entry;
    if (Array.isArray(val)) {
      accum[key] = val.length === 0 ? null : val;
    } else {
      accum[key] = val;
    }

    return accum;
  }, {});
};

console.log(emptyArraysToNulls(productDetails));

edited Jul 25, 2019 at 20:35

answered Jul 25, 2019 at 20:28

Tom O.

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3 Comments

O'Dane Brissett Over a year ago

What if the object has other keys that are not arrays? like { cislife: [], prime: [], date: 'may 1, 2019' }

Tom O. Over a year ago

Good point! - i modified the code to use Array.isArray to check and only act on array values - all other types will just be copied to the new object.

O'Dane Brissett Over a year ago

Yea this is perfect as well

Alex Lomia · Accepted Answer · 2019-07-25 20:53:39Z

2

This is a way to produce the desired array without mutating the original one:

const initialObject = {
  cislife: [],
  prime: [],
  nonArrayField: "I'm not an array, leave me alone!"
};

const resultObject = {
  ...initialObject,
  ...Object.keys(initialObject)
    // filter out keys that do not belong to empty arrays
    .filter(key => Array.isArray(initialObject[key]) && !initialObject[key].length)
    // replace empty arrays with nulls
    .reduce((acc, key) => ({ ...acc, [key]: null }), {}),
};

console.log(resultObject);

edited Jul 25, 2019 at 20:53

answered Jul 25, 2019 at 20:34

Alex Lomia

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1 Comment

O'Dane Brissett Over a year ago

Brilliant Answer

connexo · Accepted Answer · 2019-07-25 20:33:03Z

0

If you can edit the object you can use getters

var productDetails = {
  _cislife: [],
  get cislife() {
    return this._cislife.length ? this._cislife : null
  },
  _prime: [],
  get prime() {
    return this.prime.length ? this.prime : null
  },
}

console.log(productDetails.cislife)

edited Jul 25, 2019 at 20:33

connexo

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answered Jul 25, 2019 at 20:31

alfredopacino

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1 Comment

O'Dane Brissett Over a year ago

Nice idea. But a more generic solution would be preferred

Guilherme Lemmi · Accepted Answer · 2019-07-25 20:39:17Z

0

You can use getter methods, like below:

var productDetails = {
    _cislife: [],
    _prime: [],

    get cislife() {
        return this._cislife.length == 0 ? null : this._cislife;
    },

    get prime() {
        return this._prime.length == 0 ? null : this._prime;
    }
}

console.log(productDetails.cislife); // null
console.log(productDetails.prime); // null

edited Jul 25, 2019 at 20:39

answered Jul 25, 2019 at 20:32

Guilherme Lemmi

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