title: NodeJS MongoDb updateMany() with a condition?
body: <p>I want to update a MongoDb collection with an Array of JSON objects.
  However, I want the update to ignore any objects that already exist in the DB.
  Sounds easy, but the key that allows me to know if the object exists is not the '_id', but a different 'id' (or other key).
  Is that possible ?</p>
  
  <p>Currently I am using it like this:</p>
  
  <pre><code>dbHandle.collection('contents').updateMany(contents);
  </code></pre>
  
  <p>where 'contents' is the Array of JSON objects.</p>
  
  <p>Thanks in advance</p>