JS : Removing duplicate elements from an array and replacing them with updated values

Question

JS : Removing duplicate elements from an array and replacing them with updated values

I have an array that looks like this:

let arr = ['11','44','66','88','77','00','66','11','66']

Within this array, there are duplicate elements:

'11' at position 7
'66' at positions 6 and 8

I need to loop through the array to identify duplicated elements and replace them from the second occurrence with a string indicating the index of the first occurrence.

The resulting array would be:

let newarr = ['11','44','66','88','77','00','appears at 2','appears at 0','appears at 2']

As shown, the duplicates are replaced with strings like:

"appears at n" where "n" represents the index of the first occurrence

javascript typescript ecmascript-6 ecmascript-5

Answer 1

Answer №1

Give this a shot:

const counts = {}
const values = ['red','blue','green','yellow','blue','green','red']

const newValues = values.map((value, idx) => {
  if (counts[value] !== undefined) return `already counted at ${counts[value]}`
  else {
    counts[value] = idx
    return value
  }
})

console.log("Updated values: ", newValues)

Answer 2

Give this a shot:

const counts = {}
const values = ['red','blue','green','yellow','blue','green','red']

const newValues = values.map((value, idx) => {
  if (counts[value] !== undefined) return `already counted at ${counts[value]}`
  else {
    counts[value] = idx
    return value
  }
})

console.log("Updated values: ", newValues)

Answer 3

Answer №2

An innovative solution utilizing a closure with a hash table for indexing and a conditional operator

const
    data = ['11', '44', '66', '88', '77', '00', '66', '11', '66'],
    output = data.map(
        (indices => (val, index) => (indices[val] ??= index) == index ? val : `found at ${indices[val]}`)
        ({})
    );

console.log(output);

Answer 4

An innovative solution utilizing a closure with a hash table for indexing and a conditional operator

const
    data = ['11', '44', '66', '88', '77', '00', '66', '11', '66'],
    output = data.map(
        (indices => (val, index) => (indices[val] ??= index) == index ? val : `found at ${indices[val]}`)
        ({})
    );

console.log(output);

Answer 5

Answer №3

Check out this simple two-step approach:

Initialize an object to track initial occurrences
Map the original array to a new array with replacements

let numbers = ['11', '44', '66', '88', '77', '00', '66', '11', '66'];

// Record initial occurrences
const firstOccurrences = numbers.reduce((acc, val, index) => {
  if (typeof acc[val] === 'undefined') {
    acc[val] = index;
  }
  return acc;
}, {});

console.log('firstOccurrences:', firstOccurrences);

// Create a new array with replacements
const newArray = numbers.map((val, index) => {
  return (firstOccurrences[val] === index) ? val : `present at ${firstOccurrences[val]}`;
});

console.log(`newArray:`, newArray);

Answer 6

Check out this simple two-step approach:

Initialize an object to track initial occurrences
Map the original array to a new array with replacements

let numbers = ['11', '44', '66', '88', '77', '00', '66', '11', '66'];

// Record initial occurrences
const firstOccurrences = numbers.reduce((acc, val, index) => {
  if (typeof acc[val] === 'undefined') {
    acc[val] = index;
  }
  return acc;
}, {});

console.log('firstOccurrences:', firstOccurrences);

// Create a new array with replacements
const newArray = numbers.map((val, index) => {
  return (firstOccurrences[val] === index) ? val : `present at ${firstOccurrences[val]}`;
});

console.log(`newArray:`, newArray);

Answer 7

Answer №4

Answer

const numbers = ["11", "44", "66", "88", "77", "00", "66", "11", "66"].map(
  (val, index, arr) => {
    if (arr.indexOf(val, 0) !== index) {
      return `found at ${arr.indexOf(val, 0)}`;
    }
    return val;
  }
);
console.log(numbers);

Answer 8

Answer

const numbers = ["11", "44", "66", "88", "77", "00", "66", "11", "66"].map(
  (val, index, arr) => {
    if (arr.indexOf(val, 0) !== index) {
      return `found at ${arr.indexOf(val, 0)}`;
    }
    return val;
  }
);
console.log(numbers);

JS : Removing duplicate elements from an array and replacing them with updated values

Answer №1

Answer №2

Answer №3

Answer №4

Answer

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