title: Firestore Set field ID to variable
body: <p>I want to add a new field to document add call it for example <code>5</code>.
  I have variable which store the field name I want to use.</p>
  <p>So when I'm adding a new field I want to call it <code>5</code><br />
  Code:</p>
  <pre><code>let length = &quot;5&quot;;
  await firestore()
              .collection(groupID)
              .doc('jobs-list')
              .update({
                  length: licenseNumber,
              });
  </code></pre>
  <p>The problem here is that the field name is setting to <code>length</code> and I want it to be <code>5</code>.</p>