Finding duplicates in Array, Javascript

Question

I am trying to find the dupicates in an array and removing them at the duplicated index using the splice method, the code is removing the duplicates but it still leaves one duplicated item.

var removeDuplicates = function(nums) {
  let length = nums.length;
    for(let i=0;i<length;i++){
      for(let j=i+1;j<length;j++){       
        if(nums[i]==nums[j]){
          console.log(nums);
               nums.splice(j,1)
        }
      }
    } 
   return nums;
};


console.log(removeDuplicates([1,2,2,2,2,2,2]))

Try using Set, [...new Set([1,2,2,2,2,2,2])]

Som Shekhar Mukherjee
– Som Shekhar Mukherjee

2021-04-18 04:55:51 +00:00
Commented Apr 18, 2021 at 4:55 — Som Shekhar Mukherjee
– Som Shekhar Mukherjee, Commented Apr 18, 2021 at 4:55

Som Shekhar Mukherjee · Accepted Answer · 2021-04-18 05:09:20Z

1

The problem is you're looping in forward direction and simultaneously removing elements, which messes up the indices.

So, you should loop in backwards direction in this case.

var removeDuplicates = function (nums) {
  let length = nums.length;
  for (let i = length - 1; i >= 0; i--) {
    console.log(`All redundant instances of ${nums[i]} will be removed`);
    for (let j = i - 1; j >= 0; j--) {
      if (nums[i] == nums[j]) {
        nums.splice(j, 1);
      }
    }
    console.log(JSON.stringify(nums));
  }
  return nums;
};

const result = removeDuplicates([1, 1, 2, 3, 3, 2]);
console.log("Final Result", JSON.stringify(result));

For removing duplicates I would always prefer using a `Set`.

const 
  arr = [1, 1, 2, 3, 3, 2],
  result = [...new Set(arr)]

console.log(JSON.stringify(result))

edited Apr 18, 2021 at 5:09

answered Apr 18, 2021 at 5:04

Som Shekhar Mukherjee

8,1982 gold badges16 silver badges34 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Som Shekhar Mukherjee Over a year ago

@prmdpsn56 Please check if this solves your problem. Let me know if you have any issues.

Robinson De La Cruz · Accepted Answer · 2021-04-18 05:11:48Z

There are different ways to remove array duplicates.

const names = ['John', 'Paul', 'George', 'Ringo', 'John'];

let unique = [...new Set(names)];
console.log(unique); // 'John', 'Paul', 'George', 'Ringo'

const names = ['John', 'Paul', 'George', 'Ringo', 'John'];

let x = (names) => names.filter((v,i) => names.indexOf(v) === i)
x(names); // 'John', 'Paul', 'George', 'Ringo'

const names = ['John', 'Paul', 'George', 'Ringo', 'John'];

function removeDups(names) {
  let unique = {};
  names.forEach(function(i) {
    if(!unique[i]) {
      unique[i] = true;
    }
  });
  return Object.keys(unique);
}

removeDups(names); // // 'John', 'Paul', 'George', 'Ringo'

https://wsvincent.com/javascript-remove-duplicates-array/

https://medium.com/dailyjs/how-to-remove-array-duplicates-in-es6-5daa8789641c

Collectives™ on Stack Overflow

Finding duplicates in Array, Javascript

2 Answers 2

For removing duplicates I would always prefer using a `Set`.

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

For removing duplicates I would always prefer using a Set.

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related

For removing duplicates I would always prefer using a `Set`.