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Most Frequent Element in an Array using JavaScript

We will demonstrate different methods to find the most frequent element in an array in JavaScript. We will be given an array with multiple occurrences of values in that array and we have to output the maximum occurred element in that array.

Methods to Find the most frequent element in an array in JavaScript

Table of Content

Naive method using Loops and Sort function

In this method, we will sort the given array and traverse it to find the maximum occurred element.

Example:

JavaScript 
arr = [
    1, 1, 3, 5, 7, 6, 8, 5, 6, 4,
    7, 6, 0, 2, 1, 6, 8, 9, 5,
];

arr.sort((a, b) => a - b);
//console.log(arr)
let count = 1,
    max = 0,
    el;

for (let i = 1; i < arr.length; ++i) {
    if (arr[i] === arr[i - 1]) {
        count++;
    } else {
        count = 1;
    }
    if (count > max) {
        max = count;
        el = arr[i];
    }
}
console.log("The most occured element is: " + el);

Output
The most occured element is: 6

Using JavaScript Object

In this approach we will use JavaScript object to store the number and their occurences and find the element occurred most frequently.

Example:

JavaScript 
const arr = [
    1, 1, 3, 5, 7, 6, 8, 5, 6, 4,
    7, 6, 0, 2, 1, 6, 8, 9, 5,
];

obj = {};
let el,
    max = 0;
for (let i = 0; i < arr.length; i++) {
    if (!obj[arr[i]]) obj[arr[i]] = 1;
    else obj[arr[i]]++;
}

for (const i in obj) {
    if (max < obj[i]) {
        max = obj[i];
        el = i;
    }
}

console.log("The most occured element is: " + el);

Output
The most occured element is: 6

Using JavaScript Map and forEach method

In this method, we will use JavaScript Map to map the values with number of occurrences and print the maximum occurred element

Example:

JavaScript 
const arr = [
    3, 5, 7, 6, 8, 5, 6, 4, 7, 1, 
    6, 0, 2, 1, 6, 8, 9, 5, 1,
];

let m = new Map();

for (const i in arr) {
    if (!m.get(arr[i])) m.set(arr[i], 1);
    else {
        m.set(arr[i], m.get(arr[i]) + 1);
    }
}
let max = 0;
let el;
m.forEach((val, key, map) => {
    if (max < val) {
        max = val;
        el = key;
    }
});
console.log("The most occured element is: " + el);

Output
The most occured element is: 6

Using filter() and reduce()

Using filter() to get unique elements, then reduce() to find the most frequent one by comparing filtered counts. This method efficiently determines the most frequent element in an array.

Example:

JavaScript 
const array = [1, 2, 3, 2, 2, 3, 1, 4, 2];
const mostFrequent = Array.from(new Set(array)).reduce((prev, curr) =>
  array.filter(el => el === curr).length > array.filter(el => el === prev).length ? curr : prev
);
console.log(mostFrequent);

Output
2

Using reduce() and a Frequency Map

In this approach, we use the reduce() function to build a frequency map of the elements in the array. Then, we find the element with the highest frequency by iterating through this map.

Example:

JavaScript 
const arr = [
    1, 1, 3, 5, 7, 6, 8, 5, 6, 4,
    7, 6, 0, 2, 1, 6, 8, 9, 5,
];

// Create a frequency map using reduce
const frequencyMap = arr.reduce((acc, curr) => {
    acc[curr] = (acc[curr] || 0) + 1;
    return acc;
}, {});

// Find the most frequent element
let maxCount = 0;
let mostFrequentElement;
for (const [element, count] of Object.entries(frequencyMap)) {
    if (count > maxCount) {
        maxCount = count;
        mostFrequentElement = element;
    }
}

console.log("The most occurred element is: " + mostFrequentElement);

Output
The most occurred element is: 6

Using Lodash _.countBy()

Using Lodash’s _.countBy() function, you can count the occurrences of each element in an array. Then, use _.maxBy() to find the key with the highest count, identifying the most frequent element.

Example:

JavaScript 
const _ = require('lodash');

function mostFrequent(arr) {
  let freq = _.countBy(arr);
  return _.maxBy(Object.keys(freq), o => freq[o]);
}

console.log(mostFrequent([1, 2, 2, 3, 3, 3]));

Output:

3

 


Reffered: https://www.geeksforgeeks.org

JavaScript

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Category:
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Sub Category:
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