GoF Visitor

Visitor.js

class Player {
    constructor (name, points, gems) {
        this.name = name;
        this.points = points;
        this.gems = gems;
    }
    accept (visitor) {
        visitor.visit(this);
    }
    getName () {
        return this.name;
    }
    getPoints () {
        return this.points;
    }
    setPoints (pts) {
        this.points = pts;
    }
    getGems () {
        return this.gems;
    }
    setGems (gems) {
        this.gems = gems;
    }
}
class AddPoints {
    constructor() {
        this.visit = function (player) {
            player.setPoints(player.getPoints() * 1.1);
        }
    }
};
class AddGems {
    constructor() {
        this.visit = function (player) {
            player.setGems(player.getGems() + 2);
        }
    }
}

const players = [
    new Player("John", 10000, 10),
    new Player("Mary", 20000, 21),
];
const extraPoints = new AddPoints();
const extraGems = new AddGems();
for (let i = 0, len = players.length; i < len; i++) {
    const player = players[i];
    player.accept(extraPoints);
    player.accept(extraGems);
    console.log(player.getName() + ": received " + player.getPoints() +
        " extra points and " + player.getGems() + " extra gems");
}

// John: received 11000 extra points and 12 extra gems
// Mary: received 22000 extra points and 23 extra gems