title: How to push an array value in Firebase Firestore
body: <p>I am trying to push an array element but am destroying all the content there and replacing with the pushed data:</p>
  
  <pre><code>db .collection('households')
    .doc(householdId)
    .set( { users: [uid], }, { merge: true }, )
    .then(() =&gt; { resolve(); })
    .catch(() =&gt; reject());
  </code></pre>
  
  <p>I thought the merge true doesn't destroy the data that is already there? Struggling a little with the firestore api docs.</p>
  
  <p>This is the structure of my data:</p>
  
  <pre><code>households
    2435djgnfk 
      users [ 
        0: user1 
        1: user2 
      ]
  </code></pre>
  
  <p>Thank you!</p>