Remove entries from an object where the keys aren't in an array

Question

I'm trying to remove entries from an object so that it only includes those that are in an array. So I have a required array:

const required = ['accountNumber', 'packRequested', 'collectionDate']

And a touchedFields object:

const touchedFields = {
    accountNumber: true,
    sortCode: false,
    account: true,
    collectionDate: false,
    packRequested: false
}

This is what I am after:

const touchedFields = {
        accountNumber: true,
        collectionDate: false,
        packRequested: false
    }

How can this be achieved?

I've tried instead creating an array output (as I couldn't do the object), looping through each object entry, and the looping through each array key, comparing values and pushing to a new array if the values matches:

let newArr = []
for (let [key, value] of Object.entries(requiredFields)) {
    Object.keys(touchedFields).forEach((cur) => {
        if (cur == value) {
            newArr.push({cur: value})
        }
    })
}
console.log(newArr)

But even that doesn't set the values properly as it set's the key as cur and not the actual cur variable:

[{cur: 'accountNumber'}, {cur: 'packRequested'}, {cur: 'collectionDate'}]

Any help would be greatly appreciated.

Does this answer your question? [How do I create a dynamic key to be added to a JavaScript object variable](https://stackoverflow.com/questions/2462800/how-do-i-create-a-dynamic-key-to-be-added-to-a-javascript-object-variable) — computercarguy, Dec 09 '21 at 15:47

score 2 · Answer 1 · edited Dec 09 '21 at 15:45

2

Use Array.reduce method

const required = ['accountNumber', 'packRequested', 'collectionDate']

const touchedFields = {
  accountNumber: true,
  sortCode: false,
  account: true,
  collectionDate: false,
  packRequested: false
}

const result = required.reduce((acc, key) => {
  acc[key] = touchedFields[key];
  return acc;
}, {});

console.log(result);

edited Dec 09 '21 at 15:45

HoldOffHunger

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answered Dec 09 '21 at 15:44

Igor Nowosad

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epascarello · Accepted Answer · 2021-12-09T15:56:07.290

If you want to alter the orginal object, you can loop over the keys and delete the ones that are not in the required array.

const required = ['accountNumber', 'packRequested', 'collectionDate']

const touchedFields = {
  accountNumber: true,
  sortCode: false,
  account: true,
  collectionDate: false,
  packRequested: false
}

const pruneObject = (obj, keys) => Object.keys(obj).forEach(
  key => !required.includes(key) && delete obj[key]
);

pruneObject(touchedFields, required);
console.log(touchedFields);

If you do not want to alter the original object you can loop over the array and build a new object from it.

const required = ['accountNumber', 'packRequested', 'collectionDate']

const touchedFields = {
  accountNumber: true,
  sortCode: false,
  account: true,
  collectionDate: false,
  packRequested: false
}

const inclusivePick = (obj, keys) => Object.fromEntries(
  keys.map(key => [key, obj[key]])
);


const result = inclusivePick(touchedFields, required);
console.log(result);

score 2 · Answer 3 · answered Dec 09 '21 at 15:58


const required = ['accountNumber', 'packRequested', 'collectionDate']

const touchedFields = {
    accountNumber: true,
    sortCode: false,
    account: true,
    collectionDate: false,
    packRequested: false
}

let result = Object.fromEntries(
  Object.entries(touchedFields)
  .filter(([k,v]) => required.includes(k))
)

console.log(result)

Remove entries from an object where the keys aren't in an array

3 Answers3