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"}]

SSM · Answer 1 · 2022-05-16T02:20:31.043

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);

Thanks. But it should also retain any element with type "new", that is not a duplicate — Smarajit, May 16 '22 at 02:00
@Smarajit I see that you've accepted another, may I know the reason please? — SSM, May 16 '22 at 08:00

score 2 · Accepted Answer · answered May 16 '22 at 02:17

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))

score 1 · Answer 3 · answered May 16 '22 at 01:59

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));

score 1 · Answer 4 · answered Apr 03 '23 at 13:29

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);

Xupitan · Answer 5 · 2022-06-08T16:21:48.380

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)

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

5 Answers5