title: mongoose - increment a value inside an array
body: <p>I have the following schema:</p>
  
  <pre><code>var mySchema = new Schema({
    "name": String,
    "users": [
       { 
         "user_id": ObjectId,
         "counter": Number
       }]
  });
  </code></pre>
  
  <p>example of a document:</p>
  
  <pre><code>{
     "name": "Test",
     "users": [
         {
            "user_id": "aaaaaa",
            "counter": 2
         },
         {
            "user_id": "bbbbbb",
            "counter": 3
         }]
  }
  </code></pre>
  
  <p>How can i <code>findOneAndUpdate</code> a specific <code>user_id</code> and increment <code>counter</code>?</p>
  
  <p>For example: how can i find <code>Test</code> and update the <code>counter</code>of <code>user_id: bbbbb</code> in a single action? </p>