localStorage.getItem('currentUser')

var user = JSON.parse(localStorage.getItem('currentUser'));

if(user){
   console.log(user.username);
}

var user = JSON.parse(localStorage.getItem('currentUser'));
console.log(user.username);

interface IUser {
  username: string;
  password: string; // please don't do this in real code
}

function saveCurrentUser(user: IUser): void {
  localStorage.setItem('currentUser', JSON.stringify(user));
}

function getCurrentUser(): IUser {
  var userStr = localStorage.getItem('currentUser');
  try {
    return JSON.parse(userStr);
  } catch (ex) {
    return null; // or do some other error handling
  }
}

var user = { username: 'root', password: 'root' };
saveCurrentUser(user);

// elsewhere...
var savedUser = getCurrentUser();
if (savedUser) {
  console.log('Current user: ' + savedUser.username);
} else {
  console.log('Current user not found');
}