How to kill duplicates in array without using Set?

Question

How can i delete all duplicates in array without using Set (because it will disturb the order)

And why my loop with splice method doesnt work?

let result = [
  'j', 'a', 'a', 'v',
  'a', 'a', 's', 'c',
  'r', 'i', 'p', 't'
  ]
;


for (let i = 0; i < result.length; i++) {
        if (result[i] === result[i + 1]){
            result.splice(result.indexOf(result[i]), 1);
        }
}

console.log(result)  //[  "j", "v", "a",  "a",  "s",  "c", "r", "i",  "p",  "t" ]

expected output - > [  "j", "a",  "v",  "a",  "s",  "c", "r", "i",  "p",  "t" ]

"without using Set (because it will disturb the order)" sets preserve the insertion order. — VLAZ
– VLAZ, Commented Feb 24, 2021 at 9:58
The text and the expected output are conflicting. Do you actually mean you want to remove all the sequential duplicates instead of all duplicates? — Teemu
– Teemu, Commented Feb 24, 2021 at 11:29

Nina Scholz · Accepted Answer · 2021-02-24 10:01:56Z

1

You could filter the array and have a look to the predecessor.

const
    data = ['j', 'a', 'a', 'v', 'a', 'a', 's', 'c', 'r', 'i', 'p', 't'],
    result = data.filter((v, i, a) => v !== a[i - 1]);

console.log(...result);

answered Feb 24, 2021 at 10:01

Nina Scholz

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4 Comments

malarres Over a year ago

most probably the solution wanted (javascript :) , but technically this duplicates 'a' so not the solution asked

Nina Scholz Over a year ago

@malarres, but it returns the wanted pattern.

Teemu Over a year ago

@malarres No? At least the result is the same as OP's expected output. I suppose they actually wanted to ask how to remove sequential duplicates.

malarres Over a year ago

OP question: How can i delete all duplicates in array without using Set (because it will disturb the order) but yes you're right expected output - > [ "j", "a", "v", "a", "s", "c", "r", "i", "p", "t" ]

Stavros Angelis · Accepted Answer · 2021-02-24 10:10:08Z

0

Your method fails in your condition:

if (result[i] === result[i + 1])

Because you only check to see if the next item is the same as the current item and not against the entire array.

To solve this you can create a new array and push in this array only the values that are not already there, thus eliminating duplicates.

const result2 = [];
for (let i = 0; i < result.length; i += 1) {
    if (result2.indexOf(result[i])>-1) {
    continue;
  }
  result2.push(result[i]);
}

answered Feb 24, 2021 at 10:10

Stavros Angelis

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Comments

Shyam Mohan · Accepted Answer · 2021-02-24 10:14:05Z

0

I think to remove duplicate from an array write a function that do the job and return the array with unique item in it. Please find the below code that serve the propose.

function removeDuplicate(data) {
const tempArray = [];
data.forEach( (item) => {
  if (tempArray.indexOf(item) === -1) {
    tempArray.push(item);
  }
});
return tempArray;

}

let result = [ 'j', 'a', 'a', 'v', 'a', 'a', 's', 'c', 'r', 'i', 'p', 't' ];

result = removeDuplicate(result );

answered Feb 24, 2021 at 10:14

Shyam Mohan

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