A feature designed to determine the presence of duplicate numbers within an array

Question

A feature designed to determine the presence of duplicate numbers within an array

I'm attempting to develop a function that identifies duplicate numbers within an array and collects these duplicate numbers into a new array.

Here's the code I've come up with so far, but I'm encountering some challenges.

function findDuplicates(array) {
    var duplicates = [];
    for(var i = 0; i < array.length; i++) {
        if (array[i] === 1) {
            duplicates.push(array[i]);
        }
    }
    return duplicates;
}

alert(findDuplicates([1, 2, 3, 4, 5, 1]));




findDuplicates([2, 1, 1, 2, 2]); //Expected output: [1, 2, 2]. The original documents are 2, 1 and the copies are 1, 2, 2

javascript arrays

Answer 1

Answer №1

indexOf is used to find the first occurrence index of an element within an array. On the other hand, filter iterates through each element in the array and creates a new array with elements for which a specified function returns true.

function solution(array) {
    return array.filter(function(value, index) {
        return array.indexOf(value) < index;
    });
}

Answer 2

indexOf is used to find the first occurrence index of an element within an array. On the other hand, filter iterates through each element in the array and creates a new array with elements for which a specified function returns true.

function solution(array) {
    return array.filter(function(value, index) {
        return array.indexOf(value) < index;
    });
}

Answer 3

Answer №2

Within your programming challenge, you have been given two arrays: one consisting of the original numbers and another containing the result where duplicate numbers are stored.

Your initial action of iterating over the original array shows a promising start.

The variable array[i] represents the current number in the original array.

To identify whether this current number is a duplicate that has already appeared, you will need to implement the next step into your algorithm.

This may require an additional loop, possibly another array, and most likely an 'if' statement incorporated somewhere within your solution.

Answer 4

Within your programming challenge, you have been given two arrays: one consisting of the original numbers and another containing the result where duplicate numbers are stored.

Your initial action of iterating over the original array shows a promising start.

The variable array[i] represents the current number in the original array.

To identify whether this current number is a duplicate that has already appeared, you will need to implement the next step into your algorithm.

This may require an additional loop, possibly another array, and most likely an 'if' statement incorporated somewhere within your solution.

Answer 5

Answer №3

An improved and quicker alternative to the initial solution:

const findDuplicates = (array) => {
   return array.filter((value, index) => {
      return array.indexOf(value, index + 1) !== -1;
   });
}

Answer 6

An improved and quicker alternative to the initial solution:

const findDuplicates = (array) => {
   return array.filter((value, index) => {
      return array.indexOf(value, index + 1) !== -1;
   });
}

A feature designed to determine the presence of duplicate numbers within an array

Answer №1

Answer №2

Answer №3

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