title: Why Sets are considered keyed collections in JavaScript?
body: <p>I noticed that <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Keyed_collections" rel="nofollow noreferrer">Sets are being classified as keyed collections</a>, and according the definition is a:</p>
  
  <blockquote>
    <p>collections of data which are ordered by a key</p>
  </blockquote>
  
  <p>but aren't the Set keys the values indexes? I'm not sure why they aren't classified as <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Indexed_collections" rel="nofollow noreferrer">indexed collection</a> just like Arrays.</p>
  
  <p>Thanks!</p>