title: Calling function with parenthesis doesn't return anything
body: <p>When I run my code, which is supposed to print the senders name, "adopted", and then the first mentioned user</p>
  
  <pre><code>const { Client } = require('discord.js', 'async', 'discord-message-handler');
  const bot = new Client();
  const cfg = require('./config.json');
  function adoptaUser() {
      var finalString = '';
  
      finalString += '**' + (user.username) + 'adopted' + (message.mentions.member.first) + '**' + ':heart:';
  }
  
  //Skips to command here!!
  
  if(message.content.includes('hws:adopt')) {
      message.channel.send(adoptaUser(message.author.id));
  }
      });
  
  });
  
  bot.login(cfg.token);
      //I only included the code which the function uses!!
  </code></pre>
  
  <p>While no syntax errors are visible, I still get this error:</p>
  
  <pre class="lang-none prettyprint-override"><code>Bot Ready on 2 servers
  C:\Users\REMOVED\Desktop\Bot2\app.js:16
  finalString += '**' + (user.username) + 'has adopted' + (message.mentions.member.first) + '**' + ':heart:';
                         ^
  
  ReferenceError: user is not defined
  at adoptaUser (C:\Users\Moneq\Desktop\AutoRole\app.js:16:28)
  at Client.bot.on.message (C:\Users\Moneq\Desktop\AutoRole\app.js:38:30)
  at emitOne (events.js:116:13)
  at Client.emit (events.js:211:7)
  at MessageCreateHandler.handle (C:\Users\Moneq\Desktop\AutoRole\node_modules\discord.js\src\client\websocket\packets\handlers\MessageCreate.js:9:34)
  at WebSocketPacketManager.handle (C:\Users\Moneq\Desktop\AutoRole\node_modules\discord.js\src\client\websocket\packets\WebSocketPacketManager.js:103:65)
  at WebSocketConnection.onPacket (C:\Users\Moneq\Desktop\AutoRole\node_modules\discord.js\src\client\websocket\WebSocketConnection.js:333:35)
  at WebSocketConnection.onMessage (C:\Users\Moneq\Desktop\AutoRole\node_modules\discord.js\src\client\websocket\WebSocketConnection.js:296:17)
  at WebSocket.onMessage (C:\Users\Moneq\Desktop\AutoRole\node_modules\ws\lib\event-target.js:120:16)
  at emitOne (events.js:116:13)
  [nodemon] app crashed - waiting for file changes before starting...
  </code></pre>
  
  <p>Though when I try to call the function without parenthesis, I get a response from the bot though it sends the actual function and not the string.</p>
  
  <p>Any help on this?</p>