Refactoring from function to class in ES2015

Question

I am refactoring the code below into a ES2015 class (I have omitted a whole bunch of code to stick to the point):

//game.js
angular.module("klondike.game", [])
  .service("klondikeGame", ["scoring", KlondikeGame]);

function KlondikeGame(scoring) {

  this.newGame = function newGame() {
    var cards = new Deck().shuffled();
    this.newGameFromDeck(cards);
  };

  function dealTableaus(cards) {
    var tableaus = [
     new TableauPile(cards.slice(0, 1), scoring),
    ];
    return tableaus;
  }
 
}

KlondikeGame.prototype.tryMoveTopCardToAnyFoundation = function (sourcePile) {
    };

Which I converted to :

//game.js
class KlondikeGame {
  constructor(scoring) {
    this.scoring = scoring;
  }

  newGame() {
    var cards = new Deck().shuffled();
    this.newGameFromDeck(cards);
  }
         

  function dealTableaus(cards) {
    var tableaus = [
      new TableauPile(cards.slice(0, 1), this.scoring),  //<-- this throws an error     
    ];
    return tableaus;
  }

  tryMoveTopCardToAnyFoundation(sourcePile) {
    //...
  }

}

I receive the following error :

 Cannot read property 'scoring' of undefined at dealTableaus

I am using a TypeScript transpiler. What could I be missing here?

Answer 1

That should be a syntax error. You cannot put a function in the middle of your class body.

You should put it in the same place where it was declared previously: in the constructor. Same goes for the assignment of the newGame method (though I don't see any reason to put it there in the first place).

export class KlondikeGame {
    constructor(scoring) {
        this.newGame = function newGame() {
            var cards = new Deck().shuffled();
            this.newGameFromDeck(cards);
        };

        function dealTableaus(cards) {
            var tableaus = [new TableauPile(cards.slice(0, 1), scoring)];
            return tableaus;
        }
    }
    tryMoveTopCardToAnyFoundation(sourcePile) {
    }
}

Notice that scoring is a (local) variable, not a property of the instance, and only in scope inside the constructor function where it is declared as a parameter.