Find the N Largest Elements in an Array Using JavaScript

Given an array and a number n, we can find the n largest elements from the array using JavaScript.

We can find the n largest elements using the following approaches.

Approach 1: Using sort() Method

In this approach, we sort the array in descending order using the sort() method and then use slice() to extract the first n elements.

Example: In this example, we sort the array in descending order and retrieve the three largest elements.

const arr = [93, 17, 56, 91, 98, 33, 9, 38, 55, 78, 29, 81, 60];

const n = 3;

arr.sort((a, b) => b - a);

const largestElements = arr.slice(0, n);

console.log(largestElements);

[ 98, 93, 91 ]

Approach 2: Using Math.max() and filter()

In this approach, we use Math.max() to find the largest element and filter() to remove the selected element from the array. This process is repeated until n largest elements are obtained.

Example: In this example, we use Math.max() and filter() to find the three largest elements.

function getNLargestElements(arr, n) {
    const largestElements = [];

    for (let i = 0; i < n; i++) {
        const max = Math.max(...arr);

        largestElements.push(max);

        arr = arr.filter(num => num !== max);
    }

    return largestElements;
}

const array = [1, 8, 3, 5, 9, 2];

console.log(getNLargestElements(array, 3));

[ 9, 8, 5 ]

Approach 3: Using reduce() Method

In this approach, we use the reduce() method to maintain an array containing the n largest elements. Each element is added to the accumulator, sorted in descending order, and the smallest element is removed when the accumulator exceeds the required size.

Example: In this example, we use reduce() to find the three largest elements.

const array = [10, 5, 20, 8, 15];

const n = 3;

const largestElements = array.reduce((acc, curr) => {
    acc.push(curr);

    acc.sort((a, b) => b - a);

    if (acc.length > n) {
        acc.pop();
    }

    return acc;
}, []);

console.log("Largest elements:", largestElements);