title: When I'm initializing new Object it has already _id
body: <p>I didn't find information about it in google. I'm using nodejs, express, mongoose. I'm trying initializing new Object</p>
  
  <pre><code>var User = require("../modules/user/model/user");
  
  var user = new User();
  console.log(obj);
  </code></pre>
  
  <p>And console show me</p>
  
  <pre><code>{ _id: 587b9a34b03ab515e1cf01b9 }
  </code></pre>
  
  <p>I didn't save this object! Someone can say me is't normal?</p>