title: Check map key type js
body: <p>I'm trying to check the map key type to determine how i should filter it. My current approach is to check <code>myMap.keys().next().value</code> surprisingly this seems to be <code>undefined</code> regardless of whether its a string, int etc. </p>
  
  <p>I need to check if the key is either an integer or empty. So far i have tried this: </p>
  
  <pre><code>!key.next().value // for no key
  Number.isInteger(key.next().value) // for a numbered key
  </code></pre>
  
  <p>None of my if-statements are triggered with these checks.</p>