title: Mongoose.js conditional populate
body: <p>I'm working with some old data where some of the schema has a "mixed" type.</p>
  
  <p>Basically sometimes a value will be a referenced ObjectID, but other times it'll be some text (super poor design).</p>
  
  <p>I unable to correctly populate this data because of the times a non-ObjectID appears.</p>
  
  <p>So, for my actual question: Is it possible to create a populate (on a collection) that is conditional; I need to be able to tell the populate to skip those <code>other</code> values.</p>