The Code

                        
                            // get the user's message to reverse
                            function getValues() {

                                // get the text input from the page
                                let message = document.getElementById('userInput').value;

                                // validate the input: make sure the input is not empty
                                if (message.length == 0) {
                                    Swal.fire ({
                                        icon: 'error',
                                        backdrop: false,
                                        title: 'Oops!',
                                        text: 'Please enter a message to reverse'
                                    });
                                } else {
                                    // pass the input to reverseMessage() and assign its return value to a variable
                                    let revMsg = reverseMessage(message);

                                    // give the reverse message to displayessage()
                                    displayMessage(revMsg);
                                }
                            }

                            // reverse the message
                            function reverseMessage(input) { // if input = hello

                                let output = ''; // output = ['h', 'e', 'l', 'l', 'o']

                                for (let i = input.length-1; i >= 0; i--) {

                                    output += input[i]
                                }

                                // turns ['o','l','l','e','h'] into ['olleh']
                                return output;
                            }

                            // display the reverse message
                            function displayMessage(message) {

                                document.getElementById('msg').textContent = `Your message reversed is: ${message}`;

                                document.getElementById('alert').classList.remove('invisible');
                            }