在javaScript中如何导出工作。 哈希未定义的bcryptjs

Question

Let's say we have two file, user.js users.js in user.js we have. Why can we do module.exports.. we can use in it diff .js file? what does "@returns Promise If callback has been omitted" means it is from the bcrypt.genSalt function? I also have a github repo, so please take a look if you have a bit of time. after cloning it

stuck in terminal

    result { error: null,
  value:
   { email: 'max@mail.com',
     username: 'max',
     password: '1234',
     confirmationPassword: '1234' },
  then: [Function: then],
  catch: [Function: catch] }
hash undefined


const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const bcrypt = require('bcryptjs');


const userSchema = new Schema({
  email: String,
  username: String,
  password: String
});


const User = mongoose.model('user', userSchema);
module.exports = User;
module.exports.hashPassword = (password) => {
 return hash = bcrypt.genSalt(10, function(err, salt) {
    bcrypt.hash(password, salt, function(err, hash) {
    });
});
}; 

in users.js we have have

const express = require('express');
const router = express.Router();
const Joi = require('joi');
const User = require('../models/user');   



const userSchema = Joi.object().keys({
  email:Joi.string().email().required(),
  username:Joi.string().required(),
  password:Joi.string().regex(/^[a-zA-Z0-9]{3,15}$/).required(),
  confirmationPassword:Joi.any().valid(Joi.ref('password')).required()
});



router.route('/register')
  .get((req, res) => {
    res.render('register');
  })
  .post(async (req, res, next) => {
    try{
        const result =  Joi.validate(req.body,userSchema);
        console.log('result',result);

        if(result.error) {
          req.flash('error', 'Data is not valid, please try again');
          res.redirect('/users/register');
          return;
        //console.log('result',result);
      }
      //  checking if email is already taken
      const user =  await User.findOne({'email':result.value.email });
        if (user){
          req.flash('error','Email is already in use');
          res.redirect('/users/register');
          return;
        }


     // console.log('hash',hash);

      // Hash the password
      const hash = await User.hashPassword(result.value.password); 
      console.log('hash',hash);

  } catch(error) {
    next(error);
    }
  });
module.exports = router;

based the example given by bcrypt

var bcrypt = require('bcryptjs');
bcrypt.genSalt(10, function(err, salt) {
    bcrypt.hash("B4c0/\/", salt, function(err, hash) {
        // Store hash in your password DB.
    });
});

adding pic for mongo db

Answer 1

I think the problem lies in this line:

const hash = await User.hashPassword(result.value.password);

This implies that User.hashPassword(result.value.password) should be returning a promise (but it returns a reference to the wrong promise).

module.exports.hashPassword = (password) => {
    return hash = bcrypt.genSalt(10, function (err, salt) {
        bcrypt.hash(password, salt, function (err, hash) {});
    });
};

Perhaps modifying the above to return a promise may help.. Like so:

module.exports.hashPassword = (password) => {
    var salt = await bcrypt.genSalt(10);
    return bcrypt.hash(password, salt);
};

To answer your question about @returns Promise If callback has been omitted :

Bcrypt methods are asynchronous. Which means they return immediately and process in the background. When the result is available, the function makes this available to the calling code either via a callback function or a promise.

Consider the following API for genSalt from the docs:

genSalt(rounds, minor, cb)

rounds - [OPTIONAL] - the cost of processing the data. (default - 10)

minor - [OPTIONAL] - minor version of bcrypt to use. (default - b)

cb - [OPTIONAL] - a callback to be fired once the salt has been generated. uses eio making it asynchronous. If cb is not specified, a Promise is returned if Promise support is available.

  err - First parameter to the callback detailing any errors. salt - Second parameter to the callback providing the generated salt. 

What that says is genSalt can take three arguments: genSalt(rounds, minor, cb)

Sample using callbacks

If the calling code wants the result via a callback, it can pass a function which looks like function(err, salt){} as the cb parameter.

 bcrypt.genSalt(rounds, minor, function(err, salt){
     if(err){
         //Handle error
         return;
     }
     // Salt is available here
     console.log(salt);
 });

Sample using promises

If the cb parameter is not passed (null or undefined) the function returns a Promise instead.

 var promise = bcrypt.genSalt(rounds, minor);
 promise
     .then(function(salt){
         // Salt is available here
         console.log(salt);
     })
     .catch(function(err){
         // Handle error
     });