title: Is it possible to create ObjectId in Mongo shell?
body: <p>I'm updating a document with an array of embedded documents, directly in Mongo shell. I would like each of these sub-docs to have an <code>_id</code> field, but these are not created automatically as they are for top-level documents. Is there a way to simply create an new ObjectId in Mongo shell? Something along the lines of (below example is not valid):</p>
  
  <pre><code>"prop": [
    {
      "_id": new ObjectId(), // creates the objectId when executing the line
      "foo": "bar"
    }
  ]
  </code></pre>
  
  <p>The main requirement is not having to manually generate random strings for each doc to create. Is that possible?</p>