Remove duplicates from inner array of array of objects

Question

Here is my array. How can I remove duplicates in this type of structure? When I map over arr I get the values of each array nested in each object. And I want to filter the duplicated values. current output: bye hello hello The expected output should be: bye hello

[

    {
        arr: ['']
        val: "string"
    }
    {
        arr: ['bye', 'hello']
        val: "string"
    }
    {
        arr: ['hello']
        val: "string"
    }

]
    
    
myArray.map(item => item.arr.map((el, index) =>
    <p key={index}>{el}</p>       
))

you can go through this I think it will help you.

Nilesh Mishra
– Nilesh Mishra

2022-03-10 22:07:23 +00:00
Commented Mar 10, 2022 at 22:07 — Nilesh Mishra
– Nilesh Mishra, Commented Mar 10, 2022 at 22:07

vitaliyirtlach · Accepted Answer · 2022-03-10 22:00:49Z

1

I hope it will help you:

const filteredArray = useMemo(() => {
   const used = []
   
   return myArray.map(sub => {
      return { ...sub, arr:sub.arr.map(el 
    => {
      if(used.includes(el) return null
      used.push(el)
      return el
    }}
   })
}, deps)

And then in JSX:

filteredArray.map(() => ...)

edited Mar 10, 2022 at 22:00

answered Mar 10, 2022 at 21:58

vitaliyirtlach

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4 Comments

Brian Thompson Over a year ago

I hope it will help you is considered fluff, and should be left out of questions and answers. What should be included is an explanation of what your answer does. Don't make the OP and future readers figure out your code (or more likely copy/paste without understanding it).

vitaliyirtlach Over a year ago

I can give explanation personally for you. I write on my phone. And it is not simple

Brian Thompson Over a year ago

It's got to be easier to write a paragraph of explanation on a phone than it is to code...

vitaliyirtlach Over a year ago

Ok I understand will improve my answers in the future

Quentin Grisel · Accepted Answer · 2022-03-10 22:06:03Z

You could simply manage an array to filter what you want to display :

import React from 'react';
import { render } from 'react-dom';
import './style.css';

const App = () => {
  const data = [
    {
      arr: [''],
      val: 'string',
    },
    {
      arr: ['bye', 'hello'],
      val: 'string',
    },
    {
      arr: ['hello'],
      val: 'string',
    },
  ];

  const buildData = () => {
    const passedValues = [];
    return data.map((item) => {
      return item.arr.map((el) => {
        if (!passedValues.includes(el)) {
          passedValues.push(el);
          return <div>{el}</div>;
        }
      });
    });
  };

  return <div>{buildData()}</div>;
};

render(<App />, document.getElementById('root'));

Here is the repro on StackBlitz.

kaidez · Accepted Answer · 2022-03-10 22:24:34Z

All of these answer are good...I think @vitaliyirtlach has the best as its the closest to React.

I'll just put it out there that you can also loop through myArray, remove the duplicates with Set and then place them in an array that you can loop over:

    const myArray = [
    
        {
            arr: [''],
            val: "string"
        },
        {
            arr: ['bye', 'hello'],
            val: "string"
        },
        {
            arr: ['hello'],
            val: "string"
        }
    
    ]
    
    const removeDupes = () => {
      const newArr = []
      myArray.map(item => item.arr.map((el, index) =>
        newArr.push(el)     
      ))
      return [...new Set(newArr)]
    }
    
    const loopArray = removeDupes();
    
    console.log(loopArray)// logs ["","bye","hello"]

    loopArray.map((el, index) =>
      <p key={index}>{el}</p>
    ))

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