title: Cannot apply $push/$pushAll modifier to non-array, How to declare an Array in mongoose schema?
body: <p>This is my mongo schema, I'm trying to update yes/no/usersId with multiple value</p>
  
  <pre><code>var answersSchema = mongoose.Schema({
  questionId: String,
  usersId: Array,
  yes: Array,
  no: Array,
  white: Array,
  created : { type: Number, default: (new Date()).getTime() },
  });
  </code></pre>
  
  <p>and this is my operation</p>
  
  <pre><code>answer.update({
                           $addToSet: { 
                              uersId: data.userId,
                              yes: data.userId
                          } 
                      }, function(updateResponse){
                          console.log('---------------------------------------&gt; cb yes update',updateResponse)
                          result.answer = answer;
                          if (cb !== undefined &amp;&amp; cb !== null) {
                              cb(result);
                          }
                      })
  </code></pre>
  
  <p>and this is my error </p>
  
  <pre><code>Cannot apply $addToSet modifier to non-array
  </code></pre>
  
  <p>I know it's something stupid maybe I'm tired maybe someone know the problem.</p>