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javascript - 在此 JavaScript 代码中找不到错误所在。对“类”语法不太熟悉

问题描述

这是代码。这是一个随机的陌生人的任务，因为他在 IG 上看到我的帖子，所以要求我为他解决它。

// 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();

任何人都可以看到错误在哪里？我得到一个返回错误'enemy.applyDamage(dmg)'是未定义的。

这个错误是什么，我需要更多的编写而不是代码？我应该发送一些垃圾邮件吗？

标签： javascriptoopdebuggingecmascript-6

解决方案

这里的错误实际上只是在你的while循环条件下：

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

您的条件是在至少有一名玩家或至少有一名敌人时循环。所以只要其中一个数组不为空，它就会继续循环。

但是当你第一次创建this.playersand时this.enemies，它们以不同的大小开始。然后，当您从每个数组中删除一个条目时，最终其中一个数组在另一个数组之前为空。

然后，当数组为空时，您的代码var randomEnemyIndex = Math.floor(Math.random() * this.enemies.length);将评估为 0。当你这样做时this.enemies[0]，它返回未定义。当undefined被传递给weapon.attacklikeweapon.attack(randomPlayer, undefined)时，它​​会尝试调用applyDamage(dmg)，undefined这会引发您的异常。

如果您修改代码以具有以下控制台日志，您将看到问题：


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

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

      ...

你会看见：

'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，要解决此问题，您需要将条件更改为：

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

或者您需要以相同的大小启动两个阵列。

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