const STOP_COMMAND = 'Register';
const CASE_COMMAND = 'Case';
const REVERSE_COMMAND = 'Reverse';
const UPPER_CASE_COMMAND = 'Upper';
const LOWER_CASE_COMMAND = 'lower';

let usernameInput  = prompt();
let commandInput = prompt();

while (!(commandInput == STOP_COMMAND)) {

    let commandInputArr = commandInput.split(" ");
    let username = '';

    if(commandInputArr[0] == CASE_COMMAND){
        console.log(commandInputArr[1]);
        if (commandInputArr[1] == UPPER_CASE_COMMAND) {
           username = usernameInput.toUpperCase();
        } else{
           username = usernameInput.toLowerCase();
        }
        console.log(username);
        break;

    }else if(commandInputArr[0] == REVERSE_COMMAND){
        let startIndex = Number(commandInputArr[1]);
        let endIndex = Number(commandInputArr[2]);
        break;
    }

    // commandInput = prompt();
}