Code of the Programmer

Work and life as an indie Software Developer

Eric Turner

Eric Turner

Annapolis, Maryland, USA

Implementing Email Registration using Next.js & PostgreSQL

Wireframes in Assorted Colors

In the last two posts I described how I set up a PostgreSQL database on my development computer, and how all the API routes re-use the same database connection object. In this post I’ll pull it all together by creating an HTML form and API route in Next.js that saves a user’s email address and cryptographic hash of their password in the database.


I’m leaving out most of the validation and error handling in this article just to keep things as clear as possible. In a real implementation you would want to:

  • Prevent duplicate form submission
  • Validate headers (e.g. Content-Type, Accept)
  • Check for missing or malformed request body
  • Check for missing properties in the request body
  • Validate properties in the request body (e.g. email address format)
  • Handle database errors (e.g. constraint violations)

Also make sure that your web app is protected by TLS so passwords aren’t being sent from the browser to your server in plain text.

There are a lot of other features that I haven’t implemented yet that are needed for a reasonable user experience (e.g. email confirmation). I’ll probably blog about those things when I get around to implementing them.

React Component for the Registration Form

Implement a React component (e.g. components/RegistrationForm.js) that renders the registration form on a page. Some things to note about my implementation:

  • Email and password are state variables managed with the useState React hook
  • Submitting the form calls a handleSubmit function that uses fetch to POST a JSON body to the /api/users API route to create a new user

Here is my implementation of components/RegistrationForm.js:

import React, {useState} from 'react';
import fetch from 'isomorphic-unfetch';

const RegistrationForm = () => {
    const [email, setEmail] = useState('');
    const [password, setPassword] = useState('');

    const clearForm = () => {

    const handleSubmit = async (event) => {
        const response = await fetch('/api/users', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
            body: JSON.stringify({

        if (response.ok) {

    return (
        <div className='registration-form'>
            <form onSubmit={handleSubmit}>
                <label htmlFor='email'>Email</label>
                <input type='text' id='email' name='email' value={email}
                       onChange={e => setEmail(} />

                <label htmlFor='password'>Password</label>
                <input type='password' id='password' name='password' value={password}
                       onChange={e => setPassword(} />

                <button type='submit'>Register</button>
            <style jsx>{`
                padding: 0.5rem;
                form {
                    display: flex;
                    flex-direction: column;
                button {
                    margin-top: 1rem;

export default RegistrationForm;

To use this component I first import it into pages/index.js, then use it in the JSX as <RegistrationForm />.

API Route to Accept Form Submission and Save to the Database

Implement an API route (e.g. pages/api/users.js) that accepts a JSON body with email and password properties, hashes the password using bcrypt, and executes an INSERT sql statement using the shared database connection. Some things to note about my implementation:

  • Read the note on choosing salt rounds to figure out what value to use for saltRounds
  • The API route has to check which HTTP method was used (e.g. POST) and react accordingly

Here is my implementation of pages/api/users.js:

const HttpStatus = require('http-status-codes');
const bcrypt = require('bcrypt');
const db = require('../../lib/db').instance;

const hashPassword = async (password) => {
    const saltRounds = 10;
    return await bcrypt.hash(password, saltRounds);

const createUser = async (req, res) => {
    const password = await hashPassword(req.body.password);
    const user = {email:, password};
    await db.none('INSERT INTO myapp.users(${this:name}) VALUES(${this:csv})', user);

export default async (req, res) => {
    try {
        switch (req.method) {
            case 'POST':
                await createUser(req, res);
    } catch (e) {

Password Hashing

Never store passwords in plain text in your database. Also never store a weak hash of them (e.g. MD5 is weak). For my application I have decided to use bcrypt to cryptographically hash the passwords. If you want more information read How to Safely Store a Password.


Let me know if anything is unclear, you find an error, or have a recommendation for an improvement in the comments.