title: Javascript delete object property not working
body: <p>I'm running some project on MEAN.js and I've got a following problem. I want to make some user's profile calculation and the save it to database. But there's a problem with method in users model:</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>If I will send a password with my changes, it will change credentials, so user is unable to login next time. I want to delete password from user object before save, but I'm not able to do it (let's look at the comments in my code below):</p>
  
  <pre><code>exports.signin = function(req, res, next) {
      passport.authenticate('local', function(err, user, info) {
          if (err || !user) {
              res.status(400).send(info);
          } else {
              /* Some calculations and user's object changes */
              req.login(user, function(err) {
                  if(err) {
                      res.status(400).send(err);
                  } else {
                      console.log(delete user.password); // returns true
                      console.log(user.password); // still returns password :(
                      //user.save();
                      //res.json(user);
                  }
              });
          }
      })(req, res, next);
  };
  </code></pre>
  
  <p>What's wrong? Why the delete method returns true, but nothing happens? Thanks for your help :)</p>