Firebase RTDB `ref.once()` being executed multiple times
<p>Playing with firebase RTDB lately, I've been using <code>.once('value', v =&gt; ...)</code> to build the GUI of my app. The exact code below:</p>

<pre><code>&lt;script&gt;
  function onAuthCompleted(usr) {
    var salesTxRef = firebaseApp.database().ref('/salesTx').limitToLast(5);
    salesTxRef.once("value", salesTx =&gt; {
      salesTx.forEach(txRef =&gt; {
        const tx = txRef.val();
        const $item = $('&lt;li&gt;&lt;/li&gt;').html('&lt;a href="' + txRef.key + '"&gt;$' + tx.total + ' &lt;small&gt;' + tx.currencyCode + '&lt;/small&gt;&lt;/a&gt;');
        $('.main ul').append($item);
      });
    });
  }
&lt;/script&gt;
</code></pre>

<p>The problem is that if I leave the page long enough  opened, <code>.once()</code> gets called multiple times (once every 2-3 hours). Is this a bug on the javascript library? Known issue? Is there something that I'm incorrectly doing or a misunderstanding on my part?</p>