Javascript delete object property not working

问题

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 :)

回答1:

there are certain rules for delete operator in javascript

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

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

回答2:

Just do:

user.password = undefined;

instead of:

delete user.password;

and the password property will not appear at the output.

回答3:

Had a similar issue. The delete operator "was not working" when trying to delete a property from an object in a specific case. Fixed it using Lodash unset:

_.unset(user, "password");

https://lodash.com/docs/4.17.11#unset

Otherwise the delete operator does work. Just in case, delete operator docs here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete

来源：https://stackoverflow.com/questions/33239464/javascript-delete-object-property-not-working

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