Delete duplicate in array of objects [duplicate]

Question

I want to delete duplicate in array of objects but not as I found in stackoverflow questions,I want to check more than one property and verify that is not duplicate,for example :

 const input =  [
        {
          "eventUid": "0fdb73d9-629f-4151-acab-7b48c24ef2D0",
          "name": "John",
          "lastName": "Doe",
          "city": "Ukraine",
         
        },
        {
          "eventUid": "0fdb73d9-629f-4151-aBab-7b48c24ef2e0",
          "name": "Marcel",
          "lastName": "Pilate",
          "city": "Ukraine",
        },
        {
          "eventUid": "0fcc73d9-629f-4151-aBab-7b48c24ef2e0",
          "name": "John",
          "lastName": "Doe",
          "city": "Ukraine",
        }
      ]

Output shoukd be :

const input =  [
        {
          "eventUid": "0fdb73d9-629f-4151-acab-7b48c24ef2D0",
          "name": "John",
          "lastName": "Doe",
          "city": "Ukraine",
         
        },
        {
          "eventUid": "0fdb73d9-629f-4151-aBab-7b48c24ef2e0",
          "name": "Marcel",
          "lastName": "Pilate",
          "city": "Ukraine",
        }
      ]

Because I want to check name,lastName and city for each element of the array, if there are duplicate then keep only the first. Have you any idea how to check that ?

The answer with the most upvotes in the linked question is just terrible — Christian Vincenzo Traina
– Christian Vincenzo Traina, Commented Aug 17, 2023 at 12:15

Christian Vincenzo Traina · Accepted Answer · 2023-08-17 12:09:59Z

2

You can combine Array.prototype.filter and Array.prototype.findLastIndex.

The concept is that, while iterating the items, if the current index is equal to the last index then it exists twice, thus it can be removed.

Since you are comparing objects, and you want to check only 3 properties out of 4, you cannot use lastIndexOf. But instead you want to search the last index in the array with findLastIndex.

const filtered = 
  input.filter((item, index) => 
    input.findLastIndex(innerItem => 
        innerItem.name === item.name && 
        innerItem.lastName === item.lastName && 
        innerItem.city === item.city
    ) === index);

const input = [{
          "eventUid": "0fdb73d9-629f-4151-acab-7b48c24ef2D0",
          "name": "John",
          "lastName": "Doe",
          "city": "Ukraine",
         
        },
        {
          "eventUid": "0fdb73d9-629f-4151-aBab-7b48c24ef2e0",
          "name": "Marcel",
          "lastName": "Pilate",
          "city": "Ukraine",
        },
        {
          "eventUid": "0fcc73d9-629f-4151-aBab-7b48c24ef2e0",
          "name": "John",
          "lastName": "Doe",
          "city": "Ukraine",
        }
      ];
      
const filtered = input.filter((item, index) => input.findLastIndex(innerItem => innerItem.name === item.name && innerItem.lastName === item.lastName && innerItem.city === item.city) === index)

console.log(filtered);

answered Aug 17, 2023 at 12:09

Christian Vincenzo Traina

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3 Comments

0xRm Over a year ago

I think you meant to say that when the current index is NOT equal to the last index.

alainber82 Over a year ago

@0xRm Yes you're right, and when update with your idea it works!

Christian Vincenzo Traina Over a year ago

It depends on if you want to keep the first or the last match. Usually it doesn't matter, but in this case it matters since they have different eventUids

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