Solution to HackerRank Challenge: https://www.hackerrank.com/challenges/bon-appetit/problem?isFullScreen=true

bonAppetit.js

/*
 * Complete the 'bonAppetit' function below.
 *
 * The function accepts following parameters:
 *  1. INTEGER_ARRAY bill
 *  2. INTEGER k
 *  3. INTEGER b
 */

function bonAppetit(bill, k, b) {
    let actualBill = 0;
    let totalCost = 0;
    for (let item of bill) totalCost+=item;
    actualBill = (totalCost - bill[k])/2;
    
    console.log(actualBill === b ? 'Bon Appetit' : b - actualBill);
}