Question

我正在尝试从averageScore()类中调用Player类中声明的Leaderboard函数，但出现引用错误。

将我的Player类中的代码拖放到控制台中可以很好地工作，但是当我尝试从Leaderboard进行调用时，我得到了一个Reference error: add_score is undefined。

这是我的玩家班级：

class Player {

  constructor(player_id, score) {
   this.player_id = player_id;
   this.scores = [score];
   this.total = score;
   //this.average = this.total/this.scores.length;
    }

  addScore(score) {
    this.total += score;
    this.scores.push(score);
    return score;
  }

  averageScore() {
    return this.scores.length ? this.total / this.scores.length : 0;
  }

  resetScore() {
    this.scores = [];
    this.score = 0;
    }

  };

这是我的排行榜课程：

class LeaderBoard extends Player {

  add_score = (player_id, score) => {
    if (!this.player_id) {
      var newPlayer = new Player(player_id, score);
      this.player_id = newPlayer;
    } else {
      var average = this.player_id.averageScore();
      return average.toFixed(1);
    }

  };
/*...(additional functions and closing bracket excluded)*/

我希望averageScore显示为对它的add_score调用，但是却出现了参考错误-有任何想法吗？

Answer 1

LeaderBoard扩展Player毫无意义，因为LeaderBoard将包含一个Player列表

有关工作示例，请参见下面的代码

class Player {
    constructor(player_id, score) {
        this.player_id = player_id;
        this.scores = [score];
        this.total = score;
        //this.average = this.total/this.scores.length;
    }

    addScore(score) {
        this.total += score;
        this.scores.push(score);
        return score;
    }

    averageScore() {
        return this.scores.length ? this.total / this.scores.length : 0;
    }

    resetScore() {
        this.scores = [];
        this.score = 0;
    }

};
class LeaderBoard {
    constructor() {
        this.players = {};
    }
    addScore(player_id, score) {
        if (!this.players[player_id]) {
            this.players[player_id] = new Player(player_id, score);
        } else {
            this.players[player_id].addScore(score);
        }
        var average = this.players[player_id].averageScore();
        return average.toFixed(1);
    }
};
let x = new LeaderBoard();
console.log(x.addScore(1, 1)); // avg is 1 / 1 === 1
console.log(x.addScore(1, 3)); // avg is (1 + 3) / 2 === 2
console.log(x.addScore(1, 5)); // avg is (1 + 3 + 5) / 3 === 3
console.log(x.addScore(2, 7)); // avg for player 2 is 7 / 1 === 7

Answer 2

您使用的是arrow function，而不是通常的定义。这是LeaderBoard类应使用的代码：

class LeaderBoard extends Player {

  add_score(player_id, score) { //THIS LINE IS WHERE YOU WENT WRONG
    if (!this.player_id) {
      var newPlayer = new Player(player_id, score);
      this.player_id = newPlayer;
    } else {
      var average = this.player_id.averageScore();
      return average.toFixed(1);
    }

  };
/*...(additional functions and closing bracket excluded)*/

为什么我的JS类之间出现引用错误？

2 个答案: