Discord.js v14中MongoDB报Cannot read properties of undefined (reading 'push')错误修复

错误原因分析 #

报错Cannot read properties of undefined (reading 'push')说明你在对一个undefined值调用push方法，结合代码主要存在两处问题：

1. 数据库字段类型错误：创建新黑名单文档时，Words字段被赋值为单个字符串而非数组。后续查询该文档时，data.Words是字符串类型，不存在push方法，调用data.Words.push(word)会直接报错。
2. Collection取值未做兜底：blacklistedWords.get(interaction.guild.id)如果未获取到对应数据会返回undefined，直接调用push也会触发该错误。

修复步骤 #

1. 修正数据库初始化的字段类型 #

创建新文档时，将Words设置为包含单个元素的数组：

new Schema({
  Guild: interaction.guild.id,
  Words: [word] // 改为数组，而非单个字符串
}).save();

2. 对Collection的取值做兜底处理 #

在调用push前先判断是否存在对应数据，不存在则初始化空数组：

// 替换原blacklistedWords.get(...).push(word)代码
const currentBlacklist = blacklistedWords.get(interaction.guild.id) || [];
currentBlacklist.push(word);
blacklistedWords.set(interaction.guild.id, currentBlacklist);

3. 异步操作添加await（可选但推荐） #

data.save()是异步操作，添加await确保数据保存完成后再回复用户，避免数据不一致：

await data.save();

修改后的完整代码 #

const { Client, CommandInteraction, EmbedBuilder, Permissions, ApplicationCommandType } = require("discord.js");
const { Formatters } = require('discord.js');
const blacklistedWords = require("../../Collection/index.js");
const Schema = require('../../models/blacklist.js')
module.exports = {
    name: "blacklist_add",
    description: "add a word to blacklist so that the members of the server cannot use the word",
    userPerms: ['Administrator'],
    type: ApplicationCommandType.ChatInput,
    options: [{
        name: 'word',
        description: 'word to be added to the blacklist',
        type: 3,
        required: true
    }],
    /**
     *
     * @param {Client} client
     * @param {CommandInteraction} interaction
     * @param {String[]} args
     */
    run: async (client, interaction, args) => {

      const sword = interaction.options.getString('word');
      console.log(sword)
      const word = sword.toLowerCase();
      const guild = { Guild: interaction.guild.id }
      
      Schema.findOne(guild, async(err, data) => {
        if(data) {
          if(data.Words.includes(word)) return interaction.followUp(`The word already exists in the blacklist did you mean to remove it if so please use /blacklist-remove ${word} to remove the word from blacklist`)
          data.Words.push(word)
          await data.save();
          // 修复Collection的push操作
          const currentBlacklist = blacklistedWords.get(interaction.guild.id) || [];
          currentBlacklist.push(word);
          blacklistedWords.set(interaction.guild.id, currentBlacklist);
        }else {
          await new Schema({
            Guild: interaction.guild.id,
            Words: [word] // 修正为数组
          }).save();

          blacklistedWords.set(interaction.guild.id, [ word ])
        }
        const embed = new EmbedBuilder()
        .setTitle('<:donetick:951395881607893062> Blacklist system')
        .setColor('GREEN')
        .setDescription('Word added- A new word has been added to the blacklist')
        .addField('Word', `${word}`, false)
        .addField('How do I remove the word from the blacklist?', `/blacklist-remove ${word}`, false)
        
        interaction.reply({ embeds: [embed] })
      });
    },
};

内容的提问来源于stack exchange，提问作者Mohammad Zohaib Ur Rahman