How to get n largest elements from array in JavaScript ?

Here in this article, we will see that how we can find the n maximum element from the array using Javascript.

Example:

Input: arr = [1, 2, 3, 4, 5, 6], n = 3;
Output: 4, 5, 6

Explanation: Here we will see the 3 largest elements in the given array are 4, 5, 6.

Input: arr = [5, 76, 32, 98, 52, 57] n = 2;
Output: 98 , 76

There are two ways to find out the solution, we will learn both of them one by one:

Brute Force Approach: We will first make an array named largArr having a length equal to n. Then for each index of largArr, we will fill the element from the array one by one

Example: If we have n=3 then array largArr will be having a length equal to 3 then we will run for loop one by one to fill the element in the largArr.

Javascript

<script>
    var largArr = new Array();
    var arr = new Array(93, 17, 56, 91,
        98, 33, 9, 38, 55, 78, 29, 81, 60);

    function largest() {
        largArr[0] = 0;
        largArr[1] = 0;
        largArr[2] = 0;

        for (i = 0; i < arr.length; i++) {
            if (arr[i] > largArr[0]) {
                largArr[0] = arr[i];

            }
        }

        for (i = 0; i < arr.length; i++) {
            if (arr[i] > largArr[1]
                && arr[i] < largArr[0]) {
                largArr[1] = arr[i];

            }
        }

        for (i = 0; i < arr.length; i++) {
            if (arr[i] > largArr[2]
                && arr[i] < largArr[1]) {
                largArr[2] = arr[i];
            }
        }

        console.log(largArr[0]);
        console.log(largArr[1]);
        console.log(largArr[2]);
    }

    largest();
</script>

Output:

98 
93 
91

Optimized Solution: We first sort the array in decreasing order and then we run the loop for the length equal to n and print the first n largest elements.

Example:

Javascript

<script>
    var largArr = new Array();
    var arr = new Array(93, 17, 56, 91, 98,
            33, 9, 38, 55, 78, 29, 81, 60);

    findLargest3();

    function findLargest3() {
        arr.sort((a, b) => a < b ?
            1 : a > b ? -1 : 0);

        console.log(arr[0]);
        console.log(arr[1]);
        console.log(arr[2]);

        console.log(arr.slice(0, 3));
    }
</script>

Output:

 98
 93
 91
 [98,93,91]