Remove duplicate values from an array of objects in javascript [duplicate]

Question

i have an array of objects like this:

arr = [
    {label: Alex, value: Ninja},
    {label: Bill, value: Op},
    {label: Cill, value: iopop}
]

This array is composed when my react component is rendered. The i user Array.prototype.unshift for adding a desired element in the top of my array. So i write arr.unshift({label: All, value: All}). When my component first rendered my array is successfully created as i desire. But when i rerender it it shows me the array with the value {label: All, value: All} as duplicate. To be more specific it is shown something like this:

arr = [
    {label: All, value: All},
    {label: All, value: All},
    {label: Alex, value: Ninja},
    {label: Bill, value: Op},
    {label: Cill, value: iopop}
]

How can i fix this? I tried the methods described in a specific topic here but it didn't work

I've read this it is similar but not exactly duplicate. My case is different — RamAlx
– RamAlx, Commented Aug 1, 2017 at 14:02
Yeah, sure, they always are ... Please add the code you've tried. — Teemu
– Teemu, Commented Aug 1, 2017 at 14:02
Yes, they are strings just wanted to show the case i'm facing — RamAlx
– RamAlx, Commented Aug 1, 2017 at 14:05

Hassan Imam · Accepted Answer · 2018-07-11 07:02:20Z

107

You can use array#reduce and array#some.

const arr = [
    {label: 'All', value: 'All'},
    {label: 'All', value: 'All'},
    {label: 'Alex', value: 'Ninja'},
    {label: 'Bill', value: 'Op'},
    {label: 'Cill', value: 'iopop'}
]

var result = arr.reduce((unique, o) => {
    if(!unique.some(obj => obj.label === o.label && obj.value === o.value)) {
      unique.push(o);
    }
    return unique;
},[]);
console.log(result);

edited Jul 11, 2018 at 7:02

answered Aug 1, 2017 at 14:13

Hassan Imam

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2 Comments

kartik tyagi Over a year ago

Want to give 1k upvote, but you have to manage in 1 :) . Well thanks for this perfect answer

Gel Over a year ago

how do yo do this if value (instead of a string value ) is equal to some array of strings ? and I need to remove the repeated strings in there and return arr ?

chickens · Accepted Answer · 2022-04-09 12:33:27Z

25

One liner solutions:

Unique by label and value

arr.filter((v,i,a)=>a.findIndex(v2=>(v.label === v2.label && v.value===v2.value))===i)

Unique by all properties of the object:

arr.filter((v,i,a)=>a.findIndex(v2=>(JSON.stringify(v) === JSON.stringify(v2)))===i)

edited Apr 9, 2022 at 12:33

answered Oct 17, 2019 at 16:27

chickens

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2 Comments

chickens Over a year ago

v,i,a == value, index, array

djcaesar9114 Over a year ago

It doesn't work if the keys are not in the same order.

Anusha Bhat · Accepted Answer · 2020-07-04 14:37:36Z

10

This code worked for me,

const addresses = [...]; // Some array I got from async call

const uniqueAddresses = Array.from(new Set(addresses.map(a => a.id)))
 .map(id => {
   return addresses.find(a => a.id === id)
 })

answered Jul 4, 2020 at 14:37

Anusha Bhat

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1 Comment

Laurensius Adi Over a year ago

This works for 1 property (id) but not 2 as the question asked.

Azhar · Accepted Answer · 2019-12-31 11:46:22Z

1

const things = {
  thing: [
    { id: '12345', name: 'First name' },
    { id: '12345', name: 'Second name' },
    { id: '34536', name: 'Third name' }, 
  ],
};

const RemoveDuplicates = (array, key) => {
  return array.reduce((arr, item) => {
    const removed = arr.filter(i => i[key] !== item[key]);
    return [...removed, item];
  }, []);
};

console.log(RemoveDuplicates(things.thing, 'id'));

answered Dec 31, 2019 at 11:46

Azhar

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Comments

David Buck · Accepted Answer · 2020-04-04 11:59:00Z

1

function removeDuplicates(array, key) {
   let lookup = {};
   array.forEach(element => {
     lookup[element[key]] = element
   });
   return Object.keys(lookup).map(key => lookup[key]);
};

removeDuplicates(array,'objectKey');

edited Apr 4, 2020 at 11:59

David Buck

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answered Apr 4, 2020 at 11:06

Ali Akbar

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Comments

Locoder · Accepted Answer · 2020-07-24 17:57:14Z

-2

ES1 compatible :

const a = [
    {label: 'All', value: 'All'},
    {label: 'All', value: 'All'},
    {label: 'Alex', value: 'Ninja'},
    {label: 'Alex', value: 'Ninja'},
    {label: 'Alex', value: 'Ninja'}
]

for (let i = 0; i < a.length; ++i)
    for (let j = 0; j < a.length; ++j)
        if (i !== j && a[i].label === a[j].label && a[i].value === a[j].value)
            a.splice(j, 1);            
console.log(a);

answered Jul 24, 2020 at 17:57

Locoder

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