title: Check if first character is a number - Discord.js
body: <p>Working on a 'Remind Me' command, and <code>arg[0]</code> is where you input the time, using the ms node module. </p>
  
  <p>An example of the command would be <code>-remindme 5s test</code>
  I need to check if the first character (in the example it would be <code>5</code>)</p>
  
  <p>Initially, I tried:</p>
  
  <pre><code>if(isNaN(args[0])) {
     return message.channel.send('Your first input must be how long you wish the reminder to be!')
   }
  </code></pre>
  
  <p>Which in my example would be <code>5s</code>, but I only need to check the first character.</p>
  
  <p>I have been told to use <code>regex</code> but I have never touched that and have no idea how it works.</p>