问找不到引用错误问题的来源

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UnhandledPromiseRejectionWarning: ReferenceError: config is not defined

//There is code from:
//https://gist.github.com/eslachance/3349734a98d30011bb202f47342601d3

const Discord = require('discord.js');
const { prefix, token, state } = require('./config.json');
const client = new Discord.Client();
const newUsers = [];

//Say hello to every new user
client.on("guildMemberAdd", (member) => {
  const guild = member.guild;
  if (!newUsers[guild.id]) newUsers[guild.id] = new Discord.Collection();
  newUsers[guild.id].set(member.id, member.user);

  if (newUsers[guild.id].size > 10) {
    const userlist = newUsers[guild.id].map(u => u.toString()).join(" ");
    guild.channels.find(channel => channel.name === "general").send("Welcome our new users!\n" + userlist);
    newUsers[guild.id].clear();
  }
});

client.on("guildMemberRemove", (member) => {
  const guild = member.guild;
  if (newUsers[guild.id].has(member.id)) newUsers.delete(member.id);
});


//commands code
client.on("message", message => {
  if (message.author.bot) return;
  if (message.content.indexOf(config.prefix) !== 0) return;

  const args = message.content.slice(config.prefix.length).trim().split(/ +/g);
  const command = args.shift().toLowerCase();


  //if !beep, answer boop
  if (message.content === `${prefix}beep`) {
    message.channel.send('boop');
  }
//more commands
});

client.login(token);