title: Find a Mongodb document if it contains an element in the array in mongoose
body: <p>If I have a field in a mongodb document which has an array, for example:    </p>
  
  <pre><code>"tags" : [  "tag", "etc1",  "etc2",  "etc3" ]
  </code></pre>
  
  <p>Is there a way that I can select that document if it contains the element 'etc1'?
  <br/>
  If I try using the query:</p>
  
  <pre><code>db.coll.find({"tags" : { $elemMatch: { value0: 'etc1'} }})
  </code></pre>
  
  <p>but I need to know the position of the element in the array, which I don't know.
  <br/>
  I have also tried:</p>
  
  <pre><code>db.coll.find({"tags" : { $elemMatch: 'etc1' }})
  </code></pre>
  
  <p>but it needs to be an object. Is there any way of doing this?</p>
  
  <p>NB I am using mongoose but I wasn't sure how to construct the query</p>