title: Mongoose get nested document using another field
body: <p>Assume that I have a document inside a collection</p>
  <pre><code>{
    _id: &quot;3434v4vcvc254t34vtds&quot;,
    currentItemId: &quot;v281&quot;,
    items: {
        v279: [/*Some Data*/],
        v280: [/*Some Data*/],
        v281: [/*Some Data*/]
    }
  }
  </code></pre>
  <p>I need to fetch current item.<br />
  However I can do it with using two query</p>
  <pre><code>let data= await schema.findById(&quot;3434v4vcvc254t34vtds&quot;, {currentItemId});
  let itemId = `items.${data.currentItemId}`
  let item = await schema.findByID(&quot;3434v4vcvc254t34vtds&quot;, { [itemId] })
  </code></pre>
  <p><strong>I need to fetch current item using one query.</strong></p>