title: Update one field in mongoose model (node.js)
body: <p>I have a user schema where I want to update some info, like this.</p>
  
  <pre><code>User.findOne({_id: idd}, function(err, usr){
     usr.info = "some new info";
     usr.save(function(err) {
     });
  });
  </code></pre>
  
  <p>But the model has a hook on save to hash the password</p>
  
  <pre><code>UserSchema.pre('save', function(next) {
      if (this.password &amp;&amp; this.password.length &gt; 6) {
          this.salt = new Buffer(crypto.randomBytes(16).toString('base64'), 'base64');
          this.password = this.hashPassword(this.password);
      }
  
      next();
  });
  </code></pre>
  
  <p>Now when I try to save it takes the allready hased password and hash it again, any idea how to avoid this?</p>