title: Querying result from mongoose using dynamic model.find
body: <p>I need to find the results of a query with mongoose <code>find({})</code> method in Node.js with a variable containing model name.</p>
  
  <pre><code>var adSchema     =  new Schema({ schema defination });
  var Ad           =  mongoose.model('Ad', adSchema);
  var variableName = 'Ad';
  variableName.find({}).exec(function (err, adObj) {});
  </code></pre>
  
  <p>Is it possible or not? </p>
  
  <p>Thanks in advance</p>