javascript - Mongoose changes password every time I save with pre-save hook -

i'm using pre-save hook bcrypt encrypt passwords on system. works fine when creating or changing password. problem seems re-encrypt password every time change , save different field, example e-mail.

probably easier explain code. here's model:

const userschema = new schema({     email: {         type: string,         required: true,         lowercase: true,         unique: true,         trim: true     },     password: {         type: string,         required: true     } }) 

and hook:

userschema.pre('save', function(next){     const user = this;     console.log(user);     bcrypt.gensalt(10, function(err, salt){         if (err){ return next(err) }          bcrypt.hash(user.password, salt, null, function(err, hash){             if(err){return next(err)}              user.password = hash;             next();         })     }) }); 

and here's code update e-mail address:

module.exports = function(req, res){     user.findone({ _id: req.body.user}, function(err, doc){         if(err){             console.log(err);             return;         }          doc.email = req.body.data;         doc.save(function(err, returndata){             if (err){                 console.log(err);                 return;             }             res.send(returndata);         })      }) } 

so when call doc.save in final example, updates e-mail address intended re-encrypts password, meaning if user logs out, can't log in again.

can how around this?

try this:

userschema.pre('save', function(next){     if (!user.ismodified('password')) return next();      const user = this;      bcrypt.gensalt(10, function(err, salt){         if (err){ return next(err) }          bcrypt.hash(user.password, salt, null, function(err, hash){             if(err){return next(err)}              user.password = hash;             next();         })    }) });