title: Dictionary .has("key") not working, must use dictionary["key"] != "undefined" instead
body: <p>(Using javascript)</p>
  <p>I've seen some answers saying <code>dictionary.has(&quot;key&quot;)</code> will evaluate to <code>true</code> or <code>false</code> based on if the key is in the dictionary. For some reason, this hasn't worked for me at all. Only <code>dictionary[&quot;key&quot;] != &quot;undefined&quot;</code> works for me. Why is this?</p>