The code

                    
                      function fizzBuzz() {
                        let startingNumber = parseInt(document.getElementById("startNumber").value);
                        let endingNumber = parseInt(document.getElementById("endNumber").value);
                      
                        if (Number.isInteger(startingNumber) && Number.isInteger(endingNumber)) {
                          let numbers = generateFizz(startingNumber, endingNumber);
                          displayFizz(numbers);
                        } else {
                          Swal.fire({
                            icon: "error",
                            title: "Oops....",
                            text: "Only Integers are allowed for hundo!",
                          });
                        }
                      }
                      
                      function generateFizz(start, end) {
                        let numbers = [];
                      
                        for (let i = start; i <= end; i++) {
                          numbers.push(i);
                        }
                      
                        return numbers;
                      }
                      
                      function displayFizz(numbers) {
                        let templateRows = "";
                      
                        for (let i = 0; i < numbers.length; i++) {
                          let className = "";
                          let message = "";
                          let number = numbers[i];
                          if (numbers[i] % 3 == 0 && numbers[i] % 5 == 0) {
                            className = "fizzBuzz";
                            message = "FizzBuZZ";
                          } else if (numbers[i] % 5 == 0) {
                            className = "buzz";
                            message = "Buzz";
                          } else if (numbers[i] % 3 == 0) {
                            className = "fizz";
                            message = "FiZZ";
                          } else {
                            message = "" + number;
                          }
                      
                          templateRows =
                            templateRows + `${message} `;
                        }
                      
                        document.getElementById("results").innerHTML = templateRows;
                      }                         
                    
                

Our code is structured in one function

displayMessage

Prints out the mesage