Javascript class properties returning undefined

I'm learning JavaScript and I have an exercice to do. Basically it is a script that displays a contact list and also (bonus requirement) gives a way to add some contacts in it. So my approach was to create an object/class Contact and a class ContactBook that would hold a list of contacts. It requires to be initialised with 2 specific contacts at launch time.

My initial problem is that the method afficheInfos() that should return values for the instance does return undefined values. I can't put the finger on why it does that, so I made a function debugContact() to focus on my Contact class.

I don't understand why the console.log() in the constructor does not display at all. It prevent me from debugging the code. I tried to find ways to debug the code and got on the keyword debugger but I actually don't see what it does and how it works. I did a similar code as part of the course (creating instances of a class and initialize it's data) which worked fine. I can't spot any particular differences, so I'm wondering what I'm missing here. This is the WIP code in it's current state bellow:

/* 
Activité : gestion des contacts
*/

// Définir un objet contact
class Contact {
   contructor(nom, prenom) {
      this.nom = nom;
      this.prenom = prenom;

      debugger;

      console.log(this);
      //console.log("Nouveau contact ajouté: "+this.toString());
   }

   afficheInfos() {
      return `Nom: ${this.nom}, Prénom: ${this.prenom}`;
   }
}

// Définir un livre de contact
class ContactBook {


   constructor() {
      const caroleLevisse = new Contact("Carole", "Lévisse");
      const melodieNelsonne = new Contact("Mélodie", "Nelsonne");
      this.tabContacts = [caroleLevisse,melodieNelsonne];
   }

   addContact() {
      const nom = prompt("Saisissez le nom: ");
      const prenom = prompt("Saisissez le prénom: ");

      const newContact = new Contact(nom,prenom);

      this.tabContacts.push(newContact);
   }

   displayContacts() {
      var i = 0;
      //this.tabContacts.forEach(item => console.log(item.toString()));
      this.tabContacts.forEach(item => console.log("Index ["+String(i++) + "] donne " + item.afficheInfos()));
      /*
      for (var contact of this.tabContacts) {
         console.log(contact.afficheInfos());
      }; //*/

      /*
      for (var i = 0 ; i < this.tabContacts.length;i++) {
         console.log("");
      } //*/
   }
}

function main() {
   contactBook = new ContactBook();

   programContinues = true;

   while (programContinues) {
      displayMenu();
      choice = prompt("Choisissez une option: "); //TODO coder la boucle du programme

      switch(choice) {
         case "1":
            contactBook.displayContacts();
            break;
         case "2":
            contactBook.addContact();
            break;
         default:
            programContinues = false;
      }
   }

   console.log("Fin du programme.")
}

function debugContact() {
   debugContinues = true;

   while (debugContinues) {
      choice = prompt("Continuer? ");

      switch (choice) {
         case "o":
            const unPrenom = prompt("Prénom: ");
            const unNom = prompt("Nom: ");
            var contactTest = new Contact(unNom,unPrenom);
            console.log(contactTest.afficheInfos());
            break;
         default:
            debugContinues = false;
      }
   }
}

function displayMenu() {
   console.log("1) Lister les contacts.");
   console.log("2) Ajouter un contact.");
   console.log("Autre) Quitter");
}

debugContact();

//main();

Could you help me understand why it is not working properly? Kind Regards.