Discord机器人报错Cannot read properties of undefined (reading 'answer')求修复

问题场景 #

开发Discord机器人命令，功能为获取其他机器人发送的Embed标题，匹配本地谜语数据返回对应答案。运行代码时触发错误：Cannot read properties of undefined (reading 'answer')，将谜语数据移至JSON文件后无报错，但返回答案始终为undefined。

原代码：

const riddle = [
    {
      "riddle": "What has to be broken before you can use it?",
      "answer": "egg"
    },
    {
      "riddle": "I’m tall when I’m young, and I’m short when I’m old. What am I?",
      "answer": "candle"
    },
    {
      "riddle": "What month of the year has 28 days?",
      "answer": "all of them"
    },
    {
      "riddle": "What is full of holes but still holds water?",
      "answer": "sponge"
    },
    {
      "riddle": "What question can you never answer yes to?",
      "answer": "Are you asleep yet?"
    }
]
const id = args[0]
    if (isNaN(id)) return;
const msg = await message.channel.messages.fetch(id);
    if (!msg) return;
const answer = riddle.filter((obj) => obj.riddle === msg.embeds[0].title).answer
const emb = new MessageEmbed()
     .setAuthor(msg.embeds[0].title)
     .setDescription(msg.embeds[0].description)
     .setColor(msg.embeds[0].color)
message.channel.send({content: `__**Answer:**__ ${answer}`, embeds: [emb]})

错误原因 #

1. filter()返回类型错误：filter()方法始终返回数组，即使只匹配到一个元素。直接访问数组的.answer属性会得到undefined；当无匹配项时数组为空，访问空数组的.answer就会触发Cannot read properties of undefined错误。
2. 缺少边界检查：未验证目标消息是否包含Embed，若msg.embeds[0]不存在，访问.title也会导致错误。

修复方案 #

1. 用find()替代filter()：find()返回第一个匹配的对象，无匹配项时返回undefined，可直接访问其.answer属性。
2. 增加边界检查：验证消息是否包含Embed、是否匹配到对应谜语，避免运行时错误。
3. 若使用JSON文件存储谜语，直接通过require()导入即可，逻辑与本地数组一致。

修复后的完整代码：

// 若使用JSON文件，替换为 const riddle = require('./riddles.json');
const riddle = [
    {
      "riddle": "What has to be broken before you can use it?",
      "answer": "egg"
    },
    {
      "riddle": "I’m tall when I’m young, and I’m short when I’m old. What am I?",
      "answer": "candle"
    },
    {
      "riddle": "What month of the year has 28 days?",
      "answer": "all of them"
    },
    {
      "riddle": "What is full of holes but still holds water?",
      "answer": "sponge"
    },
    {
      "riddle": "What question can you never answer yes to?",
      "answer": "Are you asleep yet?"
    }
];

const id = args[0];
if (isNaN(id)) return;

const msg = await message.channel.messages.fetch(id);
if (!msg) return;

// 检查消息是否包含Embed
if (!msg.embeds || msg.embeds.length === 0) {
    return message.channel.send("目标消息中没有Embed内容");
}

const targetRiddle = msg.embeds[0].title;
// 用find()匹配第一个符合条件的谜语对象
const matchedRiddle = riddle.find(obj => obj.riddle === targetRiddle);

if (!matchedRiddle) {
    return message.channel.send("未找到对应的谜语答案");
}

const emb = new MessageEmbed()
     .setAuthor(msg.embeds[0].title)
     .setDescription(msg.embeds[0].description)
     .setColor(msg.embeds[0].color);

message.channel.send({content: `__**Answer:**__ ${matchedRiddle.answer}`, embeds: [emb]});

内容的提问来源于stack exchange，提问作者Heko