//1. Get the string from the page
                            //controller function
                            function getValue(){
                            
                                document.getElementById("alert").classList.add("invisible");
                                
                                let userString = document.getElementById("userString").value;
                                let revString = reverseString(userString);
                                displayString(revString);
                            
                            }
                            
                            //2. Reverse the string
                            //logic functiuon
                            function reverseString(userString){
                                let revString = [];
                                
                                for (let index = userString.length -1; index >= 0; index--) {
                                
                                    revString += userString[index];
                                }
                            
                                return revString;
                            }
                            
                            //3. Display the reversed message
                            //view function
                            function displayString(revString){
                                document.getElementById("msg").innerHTML = `Your string spelled backwards is  ${revString}`;
                                document.getElementById("alert").classList.remove("invisible");
                            
                            }
                        
                    

The Code is structured in one function.

Hello world.

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