auth-service.js

'use strict';

const bcrypt = require('bcrypt');
const crypto = require('crypto');

function createNewUser(db, data){
	let user = db.createUser({
		name: data.name,
		email: data.email,
		password: makeHash(data.password),
	});
	if(user) return sanitizeUserData(user);

	return false;
}

function makeHash(key, salt_length = 10){
	return bcrypt.genSalt(salt_length, function(err, salt) {
	    return bcrypt.hash(key, salt, function(err, hash) {
	    	return hash;
	    });
	});
}

function sanitizeUserData(user) {
	return user;
}

Using sync

var salt = bcrypt.genSaltSync(10);
var password = sha1(doc.password+salt);

At Async return wont work. you have to use callback or promise

function makeHash(key, salt_length = 10, callback){
    bcrypt.genSalt(salt_length, function(err, salt) {
        bcrypt.hash(key, salt, function(err, hash) {
            callback(hash);
        });
    });
}

For nested callbacks use bluebird promise.