無法在此 JavaScript 代碼中找到錯誤的位置。 對'class'語法不是很熟悉

Question

這是代碼。 這是一個隨機陌生人的任務，因為他在IG上看到了我的帖子，因此要求我為他解決。

// Player class
class Player {
  constructor(name, strength = 2, weapons) {
    this.name = name;
    this.health = 10;
    this.strength = strength;
    this.weapons = [...weapons];
  }

  applyDamage(int) {
    this.health -= int;
  }

  isAlive() {
    return this.health > 0;
  }

  attackWith() {
    let randomNum = Math.floor(Math.random() * 8);
    return this.weapons[randomNum];
  }
}

// Weapon class

class Weapon {
  constructor(name) {
    this.name = name;
    this.damage = Math.ceil(Math.random() * 5);
  }

  attack(player, enemy) {
    if (player.isAlive() && player.isAlive()) {
      let dmg = player.strength * this.damage;
      enemy.applyDamage(dmg);
      if (!enemy.isAlive()) {
        return;
      } else {
        enemy.attack(player);
      }
    }
  }
}

// Enemy class

class Enemy {
  constructor(name = "Enemy", health = 5, strength = 2) {
    this.name = name;
    this.health = health;
    this.strength = strength;
  }

  applyDamage(int) {
    this.health -= int;
  }

  isAlive() {
    return this.health > 0;
  }

  attack(player) {
    player.applyDamage(this.strength);
  }
}

// BattleSimulation class

class BattleSimulation {
  constructor() {
    this.players = [];
    this.enemies = [];
  }

  createEnemies() {
    for (let i = 0; i < 20; i += 1) {
      this.enemies[i] = new Enemy();
    }
  }

  createPlayers() {
    // Weapons
    let pencil = new Weapon("Pencil");
    let book = new Weapon("Book");
    let screwdriver = new Weapon("Screwdriver");
    let theOneRing = new Weapon("Sauron's Ring");
    let mustardGass = new Weapon("Mustard Gass");
    let bigBoy = new Weapon("A Nuke");
    let love = new Weapon("Power of Love");
    let theForce = new Weapon("The Force");

    let weaponsCache = [
      pencil,
      book,
      screwdriver,
      theOneRing,
      mustardGass,
      bigBoy,
      love,
      theForce
    ];

    // Players
    let luke = new Player("Luke", 5, weaponsCache);
    let baldingCoder = new Player("DraciVik", 10, weaponsCache);
    let trump = new Player("Trump", 1, weaponsCache);
    let kikiMakarena = new Player("Kiki Makarena", 5, weaponsCache);
    let johnWick = new Player("John Wick", 2, weaponsCache);

    this.players = [luke, baldingCoder, trump, kikiMakarena, johnWick];
  }

  run() {
    console.log("Simulating Battle");
    this.createEnemies();
    this.createPlayers();

    while (this.players.length !== 0 || this.enemies.length !== 0) {
      let randomPlayerIndex = Math.floor(Math.random() * this.players.length);
      let randomPlayer = this.players[randomPlayerIndex];
      let randomEnemyIndex = Math.floor(Math.random() * this.enemies.length);
      let randomEnemy = this.enemies[randomEnemyIndex];
      let weapon = randomPlayer.attackWith();
      weapon.attack(randomPlayer, randomEnemy);
      if (!randomPlayer.isAlive()) {
        this.players.splice(randomPlayerIndex, 1);
      }
      if (!randomEnemy.isAlive()) {
        this.enemies.splice(randomEnemyIndex, 1);
      }
    }
    console.log(this.players);
    if (this.players.length > 0) {
      return "Congratulations, you have defeated Scarlet Byle";
    }
    return "Sorry, Scarlet Byle has defeated you and conquered the free world";
  }
}

let battle = new BattleSimulation();
battle.run();

任何人都可以看到錯誤在哪里？ 我收到返回錯誤'enemy.applyDamage(dmg)'未定義。

這個錯誤是什么，我需要更多的寫作而不僅僅是代碼？ 我應該給一些信件發送垃圾郵件嗎？

Answer 1

這里的錯誤實際上只是在您的while循環條件下：

while(this.players.length !== 0 || this.enemies.length !== 0)

您的條件是在至少有一名玩家或至少有一名敵人時循環。 所以只要其中一個數組不為空，它就會繼續循環。

但是當你第一次創建this.players和this.enemies ，它們的大小不同。 然后，當您從每個數組中刪除一個條目時，最終其中一個數組在另一個數組之前為空。

那么你的代碼有var randomEnemyIndex = Math.floor(Math.random() * this.enemies.length); 當數組為空時，它將評估為 0。 當你執行this.enemies[0] ，它返回 undefined。 當undefined像weapon.attack(randomPlayer, undefined)一樣傳遞給weapon.attack ，它會嘗試在undefined上調用applyDamage(dmg) ，這會引發您的異常。

如果您修改代碼以具有以下控制台日志，您將看到問題：

    while (this.players.length !== 0 || this.enemies.length !== 0) {

      console.log("PLAYERS: " + this.players.length.toString());
      console.log("ENEMIES: " + this.enemies.length.toString());

      ...

你會看見：

'Simulating Battle'
'PLAYERS: 5'
'ENEMIES: 20'
'PLAYERS: 5'
'ENEMIES: 20'
'PLAYERS: 5'
[...]
'PLAYERS: 4'
'ENEMIES: 1'
'PLAYERS: 4'
'ENEMIES: 0'
error: Uncaught TypeError: Cannot read property 'applyDamage' of undefined

因此，要解決此問題，您需要將條件更改為：

while (this.players.length !== 0 && this.enemies.length !== 0) {

或者您需要以相同的大小啟動兩個陣列。