title: can I add new property when create new doc in mongoose?
body: <p>I have this schema (for example):</p>
  
  <pre><code>var WordSchema = new Schema({
      word: {
          type: String
      }
  });
  module.exports = mongoose.model('Word', WordSchema);
  </code></pre>
  
  <p>How I can add new property when create new doc in mongoose? something like this:</p>
  
  <pre><code>let Word = require("../models/word");
  let initWord = "hello";
  word = new Word({
     word: initWord,
     length: initWord.length
  });
  
  word.save(function(error) {
    if (error) {  
      //some code              
    } else {
      //some code              
    }
  });
  </code></pre>
  
  <p>But this does not work</p>