filter array of objects in javascript using another array of objects by id [duplicate]

Question

I have 2 arrays of objects with ids:

    const oldOffers = [
  {
    _id: "1"
  },
  {
    _id: "2"
  },
  {
    _id: "3"
  }
];

const activeOffers = [
  {
    _id: "1"
  },
  {
    _id: "5"
  }
];

I need to have a new array with objects that are present in oldOffers but are not present in activeOffers; so output will be:

filteredOffers = [{
        _id: "2"
      },
      {
        _id: "3"
      }
    ];

I solved this problem using 2 loops but in bad way, have someone any elegant solution, also that uses lodash?

What was the code for your solution and why do you think it's bad? — Mohi
– Mohi, Commented Aug 31, 2021 at 9:58

Jeremy Thille · Accepted Answer · 2021-08-31 09:59:42Z

5

Why would you need a library for that at all? It's doable with .filter and .find in one line :)

const oldOffers = [
  {_id: "1"},
  {_id: "2"},
  {_id: "3"}
];

const activeOffers = [
  {_id: "1"},
  {_id: "5"}
];

const filtered = oldOffers.filter( obj1 => !activeOffers.find(obj2 => obj1._id===obj2._id));

console.log(filtered)

answered Aug 31, 2021 at 9:59

Jeremy Thille

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4 Comments

DecPK Over a year ago

You could have store the activeOffers's _id in a Set and then use has method of set to achieve the same result in more efficient way.

Andreas Over a year ago

And there's no other question that would answer this and therefor be a valid dupe?

DecPK Over a year ago

It seems like Nina has already answered what I was saying.

Jeremy Thille Over a year ago

@Andreas I know, but basically every question is a duplicate nowadays. How are we supposed to glean some rep? :)

olayemii · Accepted Answer · 2021-08-31 10:00:54Z

2

You can solve this using the lodash differenceBy method

  const oldOffers = [
  {
    _id: "1"
  },
  {
    _id: "2"
  },
  {
    _id: "3"
  }
];

const activeOffers = [
  {
    _id: "1"
  },
  {
    _id: "5"
  }
];
_.differenceBy(oldOffers, activeOffers, '_id');

answered Aug 31, 2021 at 10:00

olayemii

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Comments

Nina Scholz · Accepted Answer · 2021-08-31 10:05:03Z

2

You could create a set of _id and filter the other array.

const
    oldOffers = [{ _id: "1" }, { _id: "2" }, {  _id: "3" }],
    activeOffers = [{ _id: "1" }, { _id: "5" }],
    active = new Set(activeOffers.map(({ _id }) => _id));
    filtered = oldOffers.filter(({ _id }) => !active.has(_id));

console.log(filtered);

answered Aug 31, 2021 at 10:05

Nina Scholz

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1 Comment

Andreas Over a year ago

Or... How to get the difference between two arrays of objects in JavaScript

DragonInTraining · Accepted Answer · 2021-08-31 10:06:47Z

0

var result = {};
var keys = Object.keys(activeOffers);

for (var key in oldOffers)
    {
    if (!keys.includes(key)) 
        {
            result[key] = oldOffers[key];
        }
    }
}

Also doable with Object.keys and includes in a single for loop. The above filtered oneliner looks really nice though.

answered Aug 31, 2021 at 10:06

DragonInTraining

3851 silver badge12 bronze badges

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