title: HTML Input Pattern Comma and Letters
body: <p>What is the correct pattern for a text input to only allow uppercase letters, lowercase letters, and commas?</p>
  
  <p>I know that this is correct for the letters:</p>
  
  <pre><code>pattern="[a-zA-Z]"
  </code></pre>
  
  <p>but I dont know how to allow commas.</p>
  
  <p>Thanks for any help!</p>