Javascript delete object property not working

Question

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:

UserSchema.pre('save', function(next) {     if (this.password && this.password.length > 6) {         this.salt = new Buffer(crypto.randomBytes(16).toString('base64'), 'base64');         this.password = this.hashPassword(this.password);     }     next(); }); 

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):

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); }; 

What's wrong? Why the delete method returns true, but nothing happens? Thanks for your help :)

Answer 1

Just do:

user.password = undefined; 

instead of:

delete user.password; 

and the password property will not appear at the output.

Answer 2

there are certain rules for delete operator in javascript

1. if the property is an own non-configurable property in "strict mode" than it will return false.

for example

x = 42;         // creates the property x on the global object var y = 43;     // creates the property y on the global object, and marks it as non-configurable  // x is a property of the global object and can be deleted delete x;       // returns true  // y is not configurable, so it cannot be deleted                 delete y;       // returns false  

2. If the object inherits a property from a prototype, and doesn't have the property itself, the property can't be deleted by referencing the object. You can, however, delete it directly on the prototype.

for example

function Foo(){} Foo.prototype.bar = 42; var foo = new Foo();  // returns true, but with no effect,  // since bar is an inherited property delete foo.bar;             // logs 42, property still inherited console.log(foo.bar); 

so, please cross check these point and for more information your can read this Link