function Student(name){
  this.name = name;
  this.assistence = ['X', 'X'];
  this.normalize = function(assistence){
    for(var i = 0; i < assistence.length; i++){
      if(assistence[i] == 1){
        this.assistence[0] = '1';
      }
      if(assistence[i] == 2){
        this.assistence[1] = '2';
      }
    }
  }
}

function Group(){
  this.students = {};
}

Group.prototype.add = function(name){
  var student = new Student(name);
  this.students[name] = student;
}

Group.prototype.asistio = function(name, assistence){
  this.students[name].normalize(assistence);
}

Group.prototype.review = function(){
  var str = "";
  for(var key in this.students){
    //console.log(key, this.students[key].assistence);
    str += key + "|" + this.students[key].assistence.join(',')+"\n";
  }
  return str;
}

var group = new Group();

group.add('Silvana');
group.add('Inti');
group.add('Steph');

group.asistio('Silvana', [1, 2]);
group.asistio('Inti', [1]);
group.asistio('Steph', [2]);

//console.log(group);
console.log(group.review());

/*
Silvana | 1, 2
Inti    | 1, -
Steph   | -, 2
*/