title: Discord.JS function error, "welcome message"
body: <p>I'm making a bot for Discord using "Discord.JS"
  I'm trying to make an intro message but I get the error "Cannot read property 'sendMessage' of undefined"</p>
  
  <p>My Code for Welcome Message:</p>
  
  <pre><code>var bot = new Discord.Client();
  
  bot.on("guildMemberAdd", member =&gt; {
      let mem = member.guild
      mem.defaultChannel.sendMessage(member.user + " welcome to the server!"); });
  </code></pre>
  
  <p>Any help?</p>