How to square the second largest number in an array

Question

I'm trying to find the 2nd largest number in an array, and square this number.

arr = [1,8,6,2,5,4,8,3,7] should return 49 (7 squared)

arr = [1,1] should return 1 (1 squared)

I've tried the code below and it works on the first array and return 49, but on the second array with [1,1] it returns NaN.

The problem is with the secondLargest variable--it returns undefined on the console.log. It may be because I'm using set, but I don't understand why it's not just returning 1 instead of undefined.

var maxArea = function(height) {

    let secondLargest = Array.from([...new Set(height)]).sort((a,b) => b-a)[1]
    console.log(secondLargest);
    
    return Math.pow(secondLargest, 2);
};

Answer 1

Set eliminates duplicates, so the array [1, 1] gets turned into [1] . There is no second element, so you get undefined when trying to access index 1 . Since this is not what you want, sort the array directly without creating a Set , or take the first element when there is no second element.

 function maxArea(height) { const sorted = [...new Set(height)].sort((a,b) => ba); return (sorted[1]?? sorted[0]) ** 2; } console.log(maxArea([1, 1])); console.log(maxArea([1,8,6,2,5,4,8,3,7]));