Remove duplicate objects from an Array

Question

I have an Array with duplicate objects, and I want to remove those duplicate objects. But I can't seem to find a proper solution for it. What is my mistake over here?

The object is as below.

{name: "login", text: "Login"}
{name: "navigation", text: "Navigation"}
{name: "landing", text: "Landing Page"}
{name: "login", text: "Login"}
{name: "navigation", text: "Navigation"}
{name: "landing", text: "Landing Page"}

Below is my code where items has the array of objects.

this.subMenuItems = this.items.reduce((acc, current) => {
  const x = acc.find(item => item.name === current.name);
  if (!x) {
    return acc.concat([current]);
  } else {
    return acc;
  }
}, []);

Also you can refer the screenshot of the Console.log of the items variable

Does this answer your question? How to remove all duplicates from an array of objects? — Heretic Monkey
– Heretic Monkey, Commented Apr 5, 2021 at 17:27
I tried this exact same code in the browser console and it works perfectly fine. Can you share some more code from your Angular component, since I believe that the issue is to be found somewhere else — kevlatus
– kevlatus, Commented Apr 5, 2021 at 17:59
Do not reinvent the wheel. Have a look at lodash uniqBy: stackoverflow.com/questions/31740155/… You can specifically install lodash.uniqBy instead of importing the whole lib: npmjs.com/package/lodash.uniqby That way to achieve your desired output with a very well tested code which probably has more capabilities. — monogate
– monogate, Commented Apr 5, 2021 at 20:07
@HereticMonkey, some help from that and some help from this question got me a solution. — oni3619
– oni3619, Commented Apr 6, 2021 at 7:42

Isaac · Accepted Answer · 2021-04-05 18:12:10Z

5

This one will assign this.subMenuItems an array containing only the first instance of each item because indexOf returns the first index where the object is found.

this.subMenuItems = this.items.filter((item, index, self) => self.indexOf(item) === index);

edited Apr 5, 2021 at 18:12

answered Apr 5, 2021 at 17:58

Isaac

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1 Comment

Shivam Singla Over a year ago

Please also consider giving the explanation about the cause of the problem in the OP's code.

Shivam Singla · Accepted Answer · 2021-04-05 19:59:12Z

1

Problem

The problem with your code is that find will always return a defined value because there is atleast one object satisfying the condition (current object itself)

Solution

One solution is the solution which @Issac gave. It's time and space complexities are O(n^2) and O(1) resp.

There is one more solution with time and space complexities O(n) and O(n) resp.

function removeDuplicates(objects) {
  const map = new Map()

  for (const obj of objects) {
    map.put(obj.name, obj)
  }

  return map.values()
}

answered Apr 5, 2021 at 19:59

Shivam Singla

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Comments

RED-ONE · Accepted Answer · 2022-11-23 09:54:49Z

please find below a function that can return the list of duplicates or a list that removes duplicates.

identifyDuplicates(data: Object[], key: string, unique: boolean = 
true) {
    const unique: Object[] = [];
    const duplicates = data.filter(x => {
        if (unique.length > 0 && (unique?.find(u => u[key] == x[key]) != null)) 
    {  return true; }
        unique.push(x);
        return false;
    });
    return unique ? unique : duplicates;
}

it can be called in two ways:

public getUnique(data: Object[], key: string) {
    return this.identifyDuplicates(data, key);
}

public getDuplicate(data: Object[], key: string) {
    return this.identifyDuplicates(data, key, false);
}

for your case:

const unique = this.getUnique(this.subMenuItems, 'name');
console.log(JSON.stringify(unique ));

if you want to get the duplicate items

const duplicates = this.getDuplicate(this.subMenuItems, 'name');
console.log(JSON.stringify(duplicates));

Gopi krishna · Accepted Answer · 2021-04-05 17:19:25Z

-1

function solve(items) {
    var m = {}
    items.forEach((obj) => {
        var name = obj.name;
        var text = obj.text;
        if (!m[name]) {
            m[name] = new Set();
        }
        m[name].add(text);

    });
    var finalItemsList = [];
    Object.keys(m).forEach((name) => {
        Array.from(m[name]).forEach((text) => {
            finalItemsList.push({
                "name": name,
                "text": text
            })
        });

    });
    return finalItemsList;

}
console.log(items);

answered Apr 5, 2021 at 17:19

Gopi krishna

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4 Comments

Shivam Singla Over a year ago

It's rather a long code. Please consirder adding some commenta to the code so that its easier for OP to integrate it in their code.

ShamPooSham Over a year ago

Not a big fan of descriptive function names are you?

oni3619 Over a year ago

Hi, thanks for taking the efforts to help me, however this solution didn't work for me. but Kudos to you for making your best effort to help

Gopi krishna Over a year ago

@oni3619, thanks man!!, can I know the test data for which the code had failed.

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