title: mongoose findOneandUpdate math operation
body: <p>I am trying to do something in Mongoose (and in general other databases) but this step I did not figure it out yet.</p>
  <p>basically I have the following query</p>
  <pre><code>const a1 = await model.findOne({type: 3}).skip(random)
  a1.views = a1.views - 1
  await a1.save()
  return a1
  </code></pre>
  <p>but what I am interested in achieving is</p>
  <pre><code>const a1 = await model.findOneAndUpdate({type: 3},{views: views--}, {new: true})
  return a1
  </code></pre>
  <p>however of course mongoose complains that views is undefined (since it was not defined before). Any suggestions how to accomplish this on the second way?</p>
  <p>cheers</p>