当未提及用户或给定用户id时，discord.js v12 Userinfo命令起作用

const Discord = require('discord.js');
const client = new Discord.Client();

client.on('message', message => {
  if (message.content.startsWith('!userinfo')) {
    const user = message.mentions.users.first() || message.author;
    const member = message.guild.member(user);

    const embed = new Discord.MessageEmbed()
      .setColor('#0099ff')
      .setTitle('User Information')
      .setThumbnail(user.displayAvatarURL())
      .addField('Username', user.username)
      .addField('ID', user.id)
      .addField('Joined Server', member.joinedAt)
      .addField('Account Created', user.createdAt);

    message.channel.send(embed);
  }
});

client.login('your-token-goes-here');