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7 ways - Remove Duplicates Array of objects

JavaScript ES 6

duplicates.js Raw #

// 0
const obj = [{ id: 1 }, { id: 2 }, { id: 3 }];

obj.forEach((o, i) => {
    if (o.id == 2) {
        obj.splice(o, 1);
    }
});

console.log(obj);




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

// 1#

const ids = arr.map(({ id }) => id);
const unique = arr.filter(({ id }, index) =>
    !ids.includes(id, index + 1));


// 2#

const unique = arr.filter((obj, index, selfArr) => {
    return index === arr.findIndex(o => obj.id === o.id); // arr === selfArr
});


 
	https://bobbyhadz.com/blog/javascript-remove-duplicates-from-array-of-objects 


// 3#

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'}]



// ✅ 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);


// #4 same as 3# but with Set

const uniqueIds = new Set()
const unique = arr.filter(element => {
	const isDuplicate = uniqueIds.has(element.id);
	uniqueIds.add(element.id);;

    if (!isDuplicate) {
        return true;
    }
    return false;
});


// #5 same as #1

const unique = arr.filter((obj, index) => {
  return index === arr.findIndex(o => obj.id === o.id);
});


// #6 same as #5 but with multiple props

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


// last duplicate objects

const unique = arr.filter((obj, index) => {
  return index === arr.findLastIndex(o => obj.id === o.id);
});


// Map solution
    const arr = [
        { id: 1, name: 'Tom' },
        { id: 1, name: 'Tom' },
        { id: 1, name: 'Alice' },
        { id: 2, name: 'Nick' },
        { id: 2, name: 'James' },
    ];

    function removeDuplicateObjects(arr, property) {
        return [...new Map(arr.map(obj => [obj[property], obj])).values()];
    }

// [ { id: 1, name: 'Alice' }, { id: 2, name: 'James' } ]
    console.log(removeDuplicateObjects(arr, 'id'));
    
    /* Same */
    const persons= [
      { id: 1, name: 'John',phone:'23' },
      { id: 2, name: 'Jane',phone:'23'},
      { id: 1, name: 'Johnny',phone:'56' },
      { id: 4, name: 'Alice',phone:'67' },
    ];
    const unique = [...new Map(persons.map((m) => [m.id, m])).values()];
    

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

    console.log(unique);