let $ = function(id){
                                return document.getElementById(id);
                            }
                            
                            //called on btn press
                            function getValue(){
                                //store user string
                                let userString = $("userString").value.toLowerCase().trim();;
                                let isPalindrome = false;
                            
                                //call function to reverse user string
                                let reversedString = `${flipString(userString)}`
                            
                                //check if reversedString is the same as userString
                                //if the string is the same forwards as backwards return true,
                                if (userString == reversedString) {
                                    isPalindrome = true;
                                } else {
                                    isPalindrome = false;
                                } 
                                
                                //display results
                                displayMessage(isPalindrome, reversedString);
                            }
                            
                            function flipString(userString){
                                //create a new array to store new reversed string in
                                let reversedString = [];
                            
                                //loop through userstring and create new array
                                for (let index = userString.length - 1; index >= 0; index--) {
                                    reversedString += userString[index];
                                }
                                return reversedString;
                            }
                            
                            function displayMessage(isPalindrome, reversedString){
                                if (isPalindrome) {
                                    $("alert").classList.remove("invisible", "alert-danger");
                                    $("alert").classList.add("alert-success");
                                    $("msg").innerHTML = `Your phrase reversed is: ${reversedString}`;
                                    $("alert-heading").innerHTML = "Well Done! You entered a palindrome!";
                                } else {
                                    $("alert").classList.remove("invisible", "alert-success");
                                    $("alert").classList.add("alert-danger");
                                    $("alert-heading").innerHTML = "Please Try Again.";
                                    $("msg").innerHTML = `Your phrase reversed is: ${reversedString}`;
                                }
                            }
                            
                        
                    

The Code is structured in one function.

Hello World

Hello world is a function that displays an alert with a message of "hello world"