how to mute someone discord.js

const Discord = require('discord.js');
const client = new Discord.Client();
const prefix = "!";
const token = ""; // Fill in your token

client.on("message", msg => {
  msg.content.startsWith(prefix + "mute") {
    
    
    // Variables
    var muteRole = msg.guild.roles.find(role => role.name.toLowerCase().includes("muted"));
    var muteChannel = msg.guild.channels.find(channel => channel.name.includes("modlogs"));
    var muteUser = msg.mentions.members.first();
    var muteReason = msg.content.slice(prefix.length + 27);
    
    
    // Conditions
    if (!msg.member.hasPermission("MANAGE_MESSAGES")) return msg.channel.send("You don't have the permissions");
    if (!muteUser) return msg.channel.send("You have to mention a valid member");
    if (!muteChannel) return msg.channel.send("There's no channel called modlogs");
    if (!muteRole) return msg.channel.send("There's no role called muted");
    if (!msg.guild.member(client.user.id).hasPermission("MANAGE_ROLES")) return msg.channel.send("I Don't have permissions");
    if (!muteReason) muteReason = "No reason given";
    
    // Embed
    var muteEmbed = new Discord.RichEmbed() 
    .setTitle("Mute")
    .addField("Muted user", muteUser)
    .addField("Reason", muteReason)
    .setFooter(`Muted by ${msg.author.tag}`)
    .setTimestamp();
    
    //Mute
    muteUser.addRole(muteRole);
    msg.channel.send(`${muteUser} has been muted`);
    muteChannel.send(muteEmbed);
    
  }
})