title: How to perform findOne query in mongoose
body: <p>i have mongoose schema named administrator</p>
  
  <pre><code>var administratorSchema = new mongoose.Schema({
  
  username : String,            
  password : String,
      active : Boolean,
      level : String
  });
  </code></pre>
  
  <p>When i try this query,i can get the result</p>
  
  <pre><code>mongoose.connect('mongodb://'+dbServer+'/'+dbName, function(connectionError) {
          var administratorModel = mongoose.model('administrators',administratorSchema);
          administratorModel.findOne({_id,111155dffxv}function(err, resad){
              console.log('into mongoose findone');
          });
  });
  ====&gt; Console output : 'into mongoose findone'
  </code></pre>
  
  <p>The problem is : when i try to change the criteria from _id to "username", mongoose dosen't work and findOne dosen't execute:</p>
  
  <pre><code>mongoose.connect('mongodb://'+dbServer+'/'+dbName, function(connectionError) {
          var administratorModel = mongoose.model('administrators',administratorSchema);
          administratorModel.findOne({'username','mohamed'}function(err, resad){
              console.log('into mongoose findone');
          });
  });
  ====&gt; Console output : ''
  </code></pre>
  
  <p>Thanks.</p>