“TypeError：无法读取未定义的属性‘id’”Discord.js 错误

Question

I am coding a Discord bot with Discord.js. I have the code below, but when I run the command I get the error: "person.roles.remove(mainrole.id); TypeError: Cannot read property 'id' of undefined"

I don't know how or what exactly to define. Any help would be appreciated, Thanks in advance.

bot.on('message', msg => {

  let args = msg.content.substring(PREFIX.length).split(" ");

  switch (args[0]) {
    case 'mute':
      let person = msg.guild.member(msg.mentions.users.first() || msg.guild.member.cache.find(args[1]))
      if (!person) {
        return msg.reply("Couldn't find that user");
      }
      let mainrole = msg.guild.roles.cache.find(role => role.name == "Member");
      let muterole = msg.guild.roles.cache.find(role => role.name === "muted");

      if (!muterole) {
        return msg.reply("Couldn't find mute role");
      }

      let time = args[2];

      if (!time){
        return msg.reply("Please specify a time")
      } 

      person.roles.remove(mainrole.id);
      person.roles.add(muterole.id);

      msg.channel.send(`@${person.user.tag} has been muted for @${ms(ms(time))}`);

      setTimeout(function (){
        person.roles.add(mainrole.id);
        person.roles.remove(muterole.id);
        msg.channel.send(`@${person.user.tag} has been unmuted`)
      }, ms(time));


      break;
  }
})

Answer 1

Seems like you are not getting this condition fulfilled, role => role.name == "Member" that's why mainrole is undefined .

You can possibly do to avoid error is:

if(mainrole && mainrole.id) {
       person.roles.remove(mainrole.id);
       person.roles.add(muterole.id);
       msg.channel.send(`@${person.user.tag} has been muted for @${ms(ms(time))}`);

       setTimeout(function(){
           person.roles.add(mainrole.id);
           person.roles.remove(muterole.id);
           msg.channel.send(`@${person.user.tag} has been unmuted`)
       }, ms(time));
}