How to usemap() method in Javascript

Approach 2: Using reduce() with sort() method

In This approach we are using the map() method to count the occurrences of elements in an array, creating a frequency map. It then converts this map into an array of [element, frequency] pairs, sorts them by frequency in descending order, and finally, extracts the top k elements, providing an efficient solution for finding k most occurring elements.

Syntax:

map((element) => { /* … */ })

Example: Below is the implementation of the above approach.

Javascript

function frequentElements(arr, k) { 
    const frequencyMap = new Map(); 
      
    // Count the occurrences of  
    // each element in the array 
    for (let i = 0; i < arr.length; i++) { 
        const num = arr[i]; 
        frequencyMap.has(num) 
            ? frequencyMap. 
                set(num, frequencyMap.get(num) + 1) 
            : frequencyMap.set(num, 1); 
    } 
      
    // Sort the entries in the frequency  
    // map by frequency in descending order 
    const sortedEntries =  
        [...frequencyMap.entries()] 
        .sort((a, b) => b[1] - a[1]); 
    const result = []; 
      
    // Extract the first k elements  
    // from the sorted entries 
    for (let i = 0; i < k &&  
            i < sortedEntries.length; i++) { 
            result.push(sortedEntries[i][0]); 
    } 
    return result; 
} 
const arr = [3, 1, 4, 4, 5, 2, 6, 1]; 
const k = 2; 
const kMostFrequent = frequentElements(arr, k); 
console.log(...kMostFrequent);

Output

1 4

JavaScript Program to Find k Most Occurrences in the Given Array

K most occurrences in an array refer to finding the K unique elements that appear the most frequently within the given array, where K is a specified integer. These are the elements with the highest frequencies in the array.

Example:

Input: arr[] = {3, 1, 4, 4, 5, 2, 6, 1}, K = 2
Output: 4 1
Explanation:
Frequency of 4 = 2, Frequency of 1 = 2
These two have the maximum frequency and 4 is larger than 1.
refer
Input: arr[] = {7, 10, 11, 5, 2, 5, 5, 7, 11, 8, 9}, K = 4
Output: 5 11 7 10
Explanation: 
Frequency of 5 = 3, Frequency of 11 = 2, Frequency of 7 = 2, Frequency of 10 = 1
These four have the maximum frequency and 5 is largest among rest.