Remove duplicate from array of objects based on value of properties in JavaScript

Question

How can I remove duplicates from an array someArray like below based on the name property given the condition that if name is the same for two elements but for one them the type is new, the original one (without type new) will be retained?

someArray = [{id: 1, name:"apple"}, {id: 2, name:"mango"}, {id: 3, name:"apple", type: "new"}, {id: 4, name:"orange"}, {id: 5, name:"orange", type: "new"}, {id: 6, name: "pineapple", type: "new"}]

to

[{id: 1, name:"apple"}, {id: 2, name: "mango"}, {id: 4, name:"orange"}, {id: 6, name: "pineapple", type: "new"}]

Code Maniac · Accepted Answer · 2022-05-16 02:17:02Z

6

You can use Map to club values by name and in case there are two values with same name just use the one without type = "new"

let someArray = [{id: 3, name:"apple", type: "new"}, {id: 1, name:"apple"}, {id: 2, name:"mango"}, {id: 4, name:"orange"}, {id: 5, name:"orange", type: "new"}, {id: 6, name: "pineapple", type: "new"}]

function getUnique(arr){
  let mapObj = new Map()
  
  arr.forEach(v => {
    let prevValue = mapObj.get(v.name)
    if(!prevValue || prevValue.type === "new"){
      mapObj.set(v.name, v)
    } 
  })
  return [...mapObj.values()]
}

console.log(getUnique(someArray))

answered May 16, 2022 at 2:17

Code Maniac

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Comments

Som Shekhar Mukherjee · Accepted Answer · 2022-05-16 02:20:31Z

5

You can use Array.prototype.reduce and filter out the items that satisfy the condition.

const 
  input = [
    { id: 1, name: "apple" },
    { id: 2, name: "mango" },
    { id: 3, name: "apple", type: "new" },
    { id: 4, name: "orange" },
    { id: 5, name: "orange", type: "new" },
    { id: 6, name: "pineapple", type: "new" },
  ],
  output = Object.values(
    input.reduce((r, o) => {
      if (!r[o.name] || (r[o.name].type === "new" && o.type !== "new")) {
        r[o.name] = o;
      }
      return r;
    }, {})
  );

console.log(output);

You can also do it using the Spread Syntax.

const 
  input = [
    { id: 1, name: "apple" },
    { id: 2, name: "mango" },
    { id: 3, name: "apple", type: "new" },
    { id: 4, name: "orange" },
    { id: 5, name: "orange", type: "new" },
    { id: 6, name: "pineapple", type: "new" },
  ],
  output = Object.values(
    input.reduce(
      (r, o) =>
        !r[o.name] || (r[o.name].type === "new" && o.type !== "new")
          ? { ...r, [o.name]: o }
          : r,
      {}
    )
  );

console.log(output);

edited May 16, 2022 at 2:20

answered May 16, 2022 at 1:57

Som Shekhar Mukherjee

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2 Comments

Smarajit Over a year ago

Thanks. But it should also retain any element with type "new", that is not a duplicate

Som Shekhar Mukherjee Over a year ago

Okay, got you! I've updated my answer, please check.

Harry Naruto · Accepted Answer · 2023-04-03 13:29:19Z

To remove the duplicates from an array of objects:

Create an empty array that will store the unique object IDs.
Use the Array.filter() method to filter the array of objects.
Only include objects with unique IDs in the new array.

// ✅ If you need to check for uniqueness based on a single property
const arr = [
  {id: 1, name: 'Tom'},
  {id: 1, name: 'Tom'},
  {id: 2, name: 'Nick'},
  {id: 2, name: 'Nick'},
];

const uniqueIds = [];

const unique = arr.filter(element => {
  const isDuplicate = uniqueIds.includes(element.id);

  if (!isDuplicate) {
    uniqueIds.push(element.id);

    return true;
  }

  return false;
});

// 👇️ [{id: 1, name: 'Tom'}, {id: 2, name: 'Nick'}]
console.log(unique);

// ------------------------------------------------------------
// ------------------------------------------------------------
// ------------------------------------------------------------

// ✅ If you need to check for uniqueness based on multiple properties

const arr2 = [
  {id: 1, name: 'Tom'},
  {id: 1, name: 'Tom'},
  {id: 1, name: 'Alice'},
  {id: 2, name: 'Nick'},
  {id: 2, name: 'Nick'},
  {id: 2, name: 'Bob'},
];

const unique2 = arr2.filter((obj, index) => {
  return index === arr2.findIndex(o => obj.id === o.id && obj.name === o.name);
});

// [
//   { id: 1, name: 'Tom' },
//   { id: 1, name: 'Alice' },
//   { id: 2, name: 'Nick' },
//   { id: 2, name: 'Bob' }
// ]
console.log(unique2);

Elvis Pimentel · Accepted Answer · 2022-05-16 01:59:59Z

2

You can iterate your array and evaluate if is 'type: new' and is not already existing, then pop out the item.

let someArray = [{
    id: 1,
    name: "apple"
}, {
    id: 2,
    name: "mango"
}, {
    id: 3,
    name: "apple",
    type: "new"
}, {
    id: 4,
    name: "orange"
}, {
    id: 5,
    name: "orange",
    type: "new"
}, {
    id: 6,
    name: "pineapple",
    type: "new"
}];
console.info('Initial value:' + JSON.stringify(someArray));
someArray.forEach(function(item, index, object) {
    if (item.type === 'new' && someArray.filter(val => val.name === item.name && !val.type)) {
        object.splice(index, 1);
    }
});

console.info('Desired Result:' + JSON.stringify(someArray));

answered May 16, 2022 at 1:59

Elvis Pimentel

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Comments

Xupitan · Accepted Answer · 2022-06-08 16:21:48Z

1

let someArray = [{id: 1, name:"apple"}, {id: 2, name:"mango"}, {id: 3, name:"apple", type: "new"}, {id: 4, name:"orange"}, {id: 5, name:"orange", type: "new"}, {id: 6, name: "pineapple", type: "new"}]
someArray.sort(function (a, b) {
  if (a.type !== 'undefined') return 1
  return 0
})
const result = someArray.reduce((resArr, currentArr) => {
  let other = resArr.some((ele) => currentArr.name === ele.name)
  if (!other) resArr.push(currentArr)
  return resArr
}, [])
console.log(result)

edited Jun 8, 2022 at 16:21

answered May 16, 2022 at 2:08

Xupitan

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Comments

fonzane · Accepted Answer · 2024-06-25 19:32:18Z

1

I like this approach

let uniqueIDs = new Set<string>();
return objectArr.filter(o => {
  if (uniqueIDs.has(o.id)) return false;
  uniqueIDs.add(o.id);
  return true;
});

edited Jun 25, 2024 at 19:32

answered Jun 25, 2024 at 19:11

fonzane

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