title: Mongoose remove clear entire array element inside a document
body: <p>Say I have a record with </p>
  
  <pre><code>{
    "_id": "3536463525325645",
    "name": "james",
    "friends": [
      "jack",
      "john",
      "jeff",
      "michael"
    ]
  }
  </code></pre>
  
  <p>I want to clear the entire array so the result would be:</p>
  
  <pre><code>{
    "_id": "3536463525325645",
    "name": "james",
    "friends": [
    ]
  }
  </code></pre>
  
  <p>I try using $pull but with no avail.
  Anyone with any suggestions?</p>