var userName = prompt('who is there?');
        switch (userName) {
            case 'Admin':
                var password = prompt('Password?');
                switch (password) {
                    case 'TheMaster':
                        alert('Welcome');
                        break;
                    // when user click on 'cancel', do nothing    
                    case null:
                        break;
                    default:
                        alert('Wrong Password');
                        break;
                }
                break;
            // when user click on 'cancel', do nothing      
            case null:
                break;
            default:
                alert("I don't know you");
                break;
        }