title: Sending a '$param' in a post request
body: <p>I am currently writing an angular, express, mongoose(monogodb) app and there is this strange behavior I am running into.</p>
  
  <p>I want to send a mongoose query to the server side so in the client side I write the query as so</p>
  
  <pre><code>var query = {
  '_id' : {'$in' : ['1958929ef']}
  };
  </code></pre>
  
  <p>This gets passed into express.js however, when I console.log it the '$in' param is not there.</p>
  
  <p>I get...</p>
  
  <pre><code>var query = {
  '_id' : {}
  }
  </code></pre>
  
  <p>When I change '$in' to just 'in' i can see there is no problem.</p>
  
  <p>Why does this happen? Is it because of sanitize? (i removed the sanitize module from angular and the issue still occurs)</p>