title: How to find a document where either one or another field matches a value?
body: <p>My model was,</p>
  
  <pre><code>var userSchema = new Schema({
      first_name : String,
      last_name : String,
      ...
  });
  </code></pre>
  
  <p>From this, I need to do search filter option. For that I am passing <code>name</code> params with value.</p>
  
  <p>Now I want to return the document  which contains  <code>first_name == name</code> or <code>last_name == name</code></p>
  
  <p>How to write the query for that?</p>