Node js: Bluebird Promisify in Mongoose middleware - node.js

Question

I have a User model that looked like this:
var Promise = require("bluebird")
var mongoose = require("mongoose");
var mongooseAlias = require('mongoose-aliasfield');
var bcrypt = Promise.promisifyAll(require('bcrypt-nodejs'));
var Schema = mongoose.Schema;
var userSchema = new Schema({
u: { type: String, required: true, trim: true, index: { unique: true }, 'alias': 'userId' },
fb: { type: String, required: true, 'alias': 'fbAccessToken' },
ap: { type: String, required: true, 'alias': 'apiAccessToken' },
f: { type: String, required: true, 'alias': 'firstName' },
l: { type: String, required: true, 'alias': 'lastName' },
e: { type: String, required: true, 'alias': 'email' }
});
// Execute before each user.save() call
userSchema.pre('save', function(callback) {
var user = this;
// return if token hasn't changed
if (!user.isModified('fb') && !user.isModified('ap'))
return callback();
// token changed so we need to hash it
bcrypt.genSalt(5, function(err, salt) {
if (err) return callback(err);
bcrypt.hash(user.fb, salt, null, function(err, hash) {
if (err) return callback(err);
user.fb = hash;
bcrypt.genSalt(5, function(err, salt) {
if (err) return callback(err);
bcrypt.hash(user.ap, salt, null, function(err, hash) {
if (err) return callback(err);
user.ap = hash;
callback();
});
});
});
});
});
userSchema.plugin(mongooseAlias);
module.exports = mongoose.model('User', userSchema);
I'm trying to learn Bluebird at the moment so I cleaned up the bcrypt code like this:
userSchema.pre('save', function(callback) {
var user = this;
// return if token hasn't changed
if (!user.isModified('fb') && !user.isModified('ap'))
return callback();
var p1 = bcrypt.genSaltAsync(5).then(function (salt) {
return bcrypt.hash(user.fb, salt, null);
}).then(function (hash) {
user.fb = hash;
});
var p2 = bcrypt.genSaltAsync(5).then(function (salt) {
return bcrypt.hash(user.ap, salt, null);
}).then(function (hash) {
user.ap = hash;
});
Promise.all(p1, p2).then(function () {
callback();
}).catch(function (err) {
callback(err);
});
});
Can I "promisify" it any further? Or rather, am I missing something here that would make it more elegant? Do I need to promisify the userSchema.pre call somehow?
Cheers

Answer 1

I thing your solution is correct. I prefere to do it a little differently (but I'm not saying that this is better):
bcrypt.genSaltAsync(5)
.then(function (salt) {
return bcrypt.hash(user.fb, salt, null);
})
.then(function (hash) {
user.fb = hash;
})
.then(function (){
return bcrypt.genSaltAsync(5);
})
.then(function (salt) {
return bcrypt.hash(user.ap, salt, null);
})
.then(function (hash) {
user.ap = hash;
})
.then(function () {
callback();
})
.catch(function (err) {
callback(err);
});
I like my solution because everything is in one flow and at first glance you know what is going on. In my solution second salt function is resolving after first. In your solution each one is resolving parallel (I dont check performance of each solution)