CODEWITHSUNDEEP
javascriptarraysduplicates
prmdpsn56
prmdpsn56

Reputation: 9

Finding duplicates in Array, Javascript

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]))

enter image description here

Upvotes: 0

Views: 528

Answers (2)

Robinson De La Cruz
Robinson De La Cruz

Reputation: 156

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

Upvotes: 0

Som Shekhar Mukherjee
Som Shekhar Mukherjee

Reputation: 8168

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))

Upvotes: 1

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