title: IE11 Intl.DateTimeFormat output won't match regex
body: <p>This is both a question and an answer so that the next time I encounter this bug and Google for an answer, I'll find it here.</p>
  
  <p>The output of</p>
  
  <pre><code>Intl.DateTimeFormat('en-US', {
    year: 'numeric',
    month: 'numeric',
    day: 'numeric',
    hour: 'numeric',
    minute: 'numeric',
    second: 'numeric',    
  })
  </code></pre>
  
  <p>Is like <code>3/7/2020 6:43:00 AM</code> in IE11. It <em>looks</em> like this regex (please do not judge my regex skills):</p>
  
  <pre><code>/:[0-9]{2}:[0-9]{2}/g
  </code></pre>
  
  <p>Should match the <code>:43:00</code> portion, and it does in other browsers. But it does not in IE11. What gives?</p>