من به این روش حل کردم دوستان 

var input = prompt("Whos there ??");
           switch (input){
                case "Admin":
                   var pass = prompt ("Password ??");
                   switch (pass){
                        case "TheMaster":
                           alert("Welcome !!");
                           break;
                        case "Cancel":
                            alert("Canceled Pass");
                            break;
                        default:
                            alert("Wrong password");
                            break;
                   }
                   break;
                case "Cancel":
                    alert("Canceled User");
                    break;
                default:
                    alert("I dont know you !");
                    break;       
           }