javascript - 读取对象内部的对象为未定义

Question

我正在尝试制作一款口袋妖怪风格的游戏，您可以在其中孵化和进化龙。大多数龙都有一条它们进化成的更强大的龙。

https://jsbin.com/pulawoz/15/edit?html,js,output

当我创建“evolve”函数时，我遇到了麻烦。它始终将正在进化的龙 (dragonToEvolve) 的 evolvesInto 属性读取为未定义。

你可以在这里看到问题代码:

var dragons = [];
var enemyDragon;

function Dragon(name, ATK, maxATK, HP, maxHP, normalPowers, continuousPowers,
    responsePowers, type, cry, evolvesInto, numberOfAttacks) {

    this.name = name;
    this.ATK = ATK;
    this.HP = HP;
    this.maxATK = maxATK;
    this.maxHP = maxHP;
    this.normalPowers = normalPowers;
    this.continuousPowers = continuousPowers;
    this.responsePowers = responsePowers;     
    this.type = type;        
    this.cry = cry;        
    this.evolvesInto = evolvesInto;        
    this.numberOfAttacks = numberOfAttacks        
}

// Dragons

var lusterDragon = new Dragon("Luster Dragon", 1900, 1900, 2500, 2500, [],
   [], [], "Wind", "Shining Emerald Blast! Sha-shing!", lusterDragon2, 1);

var lusterDragon2 = new Dragon("Luster Dragon 2", 2400, 2400, 3100, 3100, [], 
    [], [], "Wind", "Ultimate Emerald Blast! Shaka-shing!", null, 1);

var wattailDragon = new Dragon("Wattail Dragon", 2500, 2500, 3000, 3000, [], 
    [], [], "Light", "Shock Bolt! KRAKA-THOOM!", null, 1);

var babyDragon = new Dragon("Baby Dragon", 1200, 1200, 1800, 1800, [], [], 
    [], "Wind", "Mini Fang! Chomp!", thousandDragon, 1);

var thousandDragon = new Dragon("Thousand Dragon", 2400, 2400, 3500, 3500, 
    [], [], [], "Wind", "Thousand Fang! Chomp!", null, 1);

var alexandriteDragon = new Dragon("Alexandrite Dragon", 2000, 2000, 2400, 
    2400, [], [], [], "Light", "Diamond Blast! Sha-shing!", null, 1);

var hyozanryu = new Dragon("Hyozanryu", 2100, 2100, 3800, 3800, [], [], [], 
    "Light", "Diamond Blade! Shing!", lightEndDragon, 1);

var labradoriteDragon = new Dragon("Labradorite Dragon", 0, 0, 4500, 4500, 
    [], [], [], "Dark", "...", darkEndDragon, 1);

var darkEndDragon = new Dragon("Dark End Dragon", 2600, 2600, 4000, 4000, 
    [darkDrain], [], [], "Dark", "Infernal Force! OOOOOOOOOM!", null, 1);

var lightEndDragon = new Dragon("Light End Dragon", 2600, 2600, 4000, 
    4000[lightBlast], [], [], "Light", "Shining Force! OOOOOOOOM!", null, 1)

var cyberDragon = new Dragon("Cyber Dragon", 2100, 2100, 2700, 2700, [], [], 
    [], "Light", "Cyber Burst! FWOOOOM!", cyberTwinDragon, 1);

var cyberTwinDragon = new Dragon("Cyber Twin Dragon", 2800, 2800, 3600, 3600, 
    [], [], [], "Light", "Cyber Burst v2! FWOOOOM!", cyberEndDragon, 2);

var cyberEndDragon = new Dragon("Cyber End Dragon", 4000, 4000, 5000, 5000, 
    [cyberPierce], [], [], "Light", "Ultimate Cyber Burst! FWOOOOOOOOOOOOOOOOOOOOM!", 
    null, 1)

var cyberDragonDrei = new Dragon("Cyber Dragon Drei", 1800, 1800, 2600, 2600, 
    [], [], [], "Light", "Cyber Burst! FWOOM!", cyberDragonNova, 1);

var cyberDragonNova = new Dragon("Cyber Dragon Nova", 2100, 2100, 3000, 3000, 
    [cyberUpgrade], [], [], "Light", "Helios Cyber Burst! FWOOOM!",
    cyberDragonInfinity, 1);

var cyberDragonInfinity = new Dragon("Cyber Dragon Infinity", 2100, 2100, 
    3000, 3000, [cyberAbsorb], [cyberGain], [cyberCancel], "Light", 
    "Infinite Cyber Burst! FWOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOM!", 
    null, 1);

var evolveAsk = function(){
    var selectedDragon = prompt("Which dragon do you want to evolve?");
    var dragonToEvolve = selectedDragons[selectedDragon-1];

    console.log(dragonToEvolve.name + " selected.");

    dragons.shift(dragonToEvolve);

    console.log(dragonToEvolve);

    dragons.push(dragonToEvolve.evolvesInto);            
};

var evolvePrint = function(){
    console.log(selectedDragons);          
    var i = 0;

    for (i = 0; i < dragons.length; i++) { 
        if(dragons[i].evolvesInto !== null){
            console.log("Press " + (i+1) + " to select " + dragons[i].name);
            selectedDragons.push(dragons[i]);
        }
    }          
};

var selectedDragons = [];

var evolve = function(){          
    selectedDragons = [];
    evolvePrint();

    setTimeout(function(){
        evolveAsk();
    },1000);
}

我是菜鸟，所以我可能遗漏了一些明显的东西。非常感谢任何帮助!

附言 如果你想测试它，输入这些命令:

dragons.push(lusterDragon);
evolve();

然后按1回车。

Answer 1

您的 evolvesInto into 属性有一些混淆之处。对于 lusterDragon 它是一个数组，对于其他龙它是一个变量。

我们需要保持一致。将所有变量转换为字符串的最简单解决方案:

var lusterDragon = new Dragon("Luster Dragon", 1900, 1900, 2500, 2500, [], [], [], "Wind", "Shining Emerald Blast! Sha-shing!", ' lusterDragon2', 1);

如果您想将其保留为嵌套对象(我认为您想要)，您需要先定义 lusterDragon2，例如 Fiddle:https://jsbin.com/nevaqicaro/1/edit

就像现在一样，它将是未定义的，因为变量 lusterDragon2 尚未定义。