Discord Bot unexpectedly exits with error when successfully banning someone

The problem that I have is with the case “ban”. When I go “+ban” and then mention the user, it works. The user is banned and the message is sent but then it exits with a message error about the Discord API and permission, even though I have admin permission for the bot.

And when I don’t mention anyone, it does what it’s supposed to do and just gives out the “There is no one to ban.” message but it then exits with an error (Error [BAN_RESOLVE_ID]: Couldn't resolve the user ID to ban.). I need to rerun the code to get the bot started again.

Do you know how to to keep the bot running with no issues?

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

const prefix = "+";

client.on('ready', () => {
  console.log(`Logged in as ${client.user.tag}!`);

});


client.on('message', msg => {
    const { content } = msg;
    let latency = Date.now() - msg.createdTimestamp;
    let latencyOfAPI = Math.round(client.ws.ping);
    const user = msg.mentions.users.first();
    let banMember = msg.guild.members.ban(user);
    
    if (!content.startsWith(prefix)) return;

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

        case "ping" : {

            msg.reply("This is the latency between the message and the response: " + latency + "."  + "nThis is the API latency: " + latencyOfAPI + ".");

            break;
        } 

        case "pong" : {

            msg.reply("ping");
            break
        }

        case "ban" : {
            if (user) {
               banMember;
               msg.reply("The user " + user + " has been banned.") 
            } else {
                 return msg.reply("There is no one to ban.")
            }
            
            break
        }

    }
});
client.login(.....)

Answer

The first problem is that you try to ban someone even if there is no member mentioned or if there was no ban command. You try to define a banMember variable using let banMember = msg.guild.members.ban(user) but it calls the ban() method before you check if the command is “ban”. You need to move this ban() method inside the switch statement.

Second, you try to ban a User. msg.mentions.users.first() returns a User if there’s someone mentioned. Users don’t have a ban() method, only GuildMembers have.

Instead of msg.mentions.users you should use msg.mentions.members.

Your code should look something like this:

client.on('message', (msg) => {
  const { content } = msg;

  if (!content.startsWith(prefix)) return;

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

  switch (command) {
    case 'ping': {
      let latency = Date.now() - msg.createdTimestamp;
      let latencyOfAPI = Math.round(client.ws.ping);

      msg.reply(
        `This is the latency between the message and the response: ${latency}.nThis is the API latency: ${latencyOfAPI}.`,
      );
      break;
    }

    case 'pong': {
      msg.reply('ping');
      break;
    }

    case 'ban': {
      const member = msg.mentions.members.first();

      if (!member) return msg.reply('There is no one to ban.');

      msg.guild.members
        .ban(member)
        .then(() => msg.reply(`The member ${member} has been banned.`))
        .catch(console.error);
      break;
    }
  }
});