title: Firestore - Delete a field inside an object
body: <p>I'm using Firestore and I would like to delete a field that is in a specific object.
  I can delete a field in a document thanks to : </p>
  
  <pre><code>fieldName: firebase.firestore.FieldValue.delete()
  </code></pre>
  
  <p>But if I have an object like : </p>
  
  <pre><code>songList {
  songName1: "HelloWorld",
  songName2: "AnotherSong",
  songName3: "andTheLastOne"
  }
  </code></pre>
  
  <p>In order to delete the field songName3, I won't be able to do something like : </p>
  
  <pre><code>songList.songName3: firebase.firestore.FieldValue.delete()
  </code></pre>
  
  <p>Is there a way to delete a field inside an object ? Or should I delete the whole object, rebuild it without the 3rd field and save it ?</p>
  
  <p>Thanks in advance,</p>