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March 30, 2020

5 min read

How to Authenticate your Next.js application using Open Source Headless CMS Strapi

In this tutorial, we'll learn about how to authenticate a front-end application using Next.js and Strapi.

Table of Contents

Getting started with authentication

First, we'll build the authentication in our frontend application. To do that, we'll add a new sign up page.

frontend/pages/sign-up.js

import React, { useState } from "react";
import Head from "next/head";
import axios from "axios";

import "../public/assets/styles/tailwind.css";

const SignUp = () => {
  const [username, setUsername] = useState("");
  const [email, setEmail] = useState("");
  const [password, setPassword] = useState("");

  const handleSubmit = async (e) => {
    e.preventDefault();

    const res = await axios.post("http://localhost:1337/auth/local/register", {
      username,
      email,
      password,
    });

    // res.data contains data for authenticated user
    console.log(res.data);
  };

  return (
    <div>
      <Head>
        <title>Sign Up</title>
        <link rel="icon" href="/favicon.ico" />
      </Head>
      <div className="flex justify-center items-center h-screen bg-gray-100">
        <div className="w-full max-w-md">
          <form className="bg-white shadow-lg rounded p-8">
            <div className="mb-4">
              <label
                className="block text-gray-700 text-sm font-bold mb-2"
                htmlFor="username"
              >
                Username
              </label>
              <input
                className="appearance-none border rounded w-full p-3 text-gray-700 leading-tight focus:outline-none focus:shadow-outline"
                id="username"
                type="text"
                placeholder="John Doe"
                value={username}
                onChange={(e) => setUsername(e.target.value)}
              />
            </div>
            <div className="mb-4">
              <label
                className="block text-gray-700 text-sm font-bold mb-2"
                htmlFor="email"
              >
                Email Address
              </label>
              <input
                className="appearance-none border rounded w-full p-3 text-gray-700 leading-tight focus:outline-none focus:shadow-outline"
                id="email"
                type="email"
                placeholder="john@doe.com"
                value={email}
                onChange={(e) => setEmail(e.target.value)}
              />
            </div>
            <div className="mb-8">
              <label
                className="block text-gray-700 text-sm font-bold mb-2"
                htmlFor="password"
              >
                Password
              </label>
              <input
                className="appearance-none border rounded w-full p-3 text-gray-700 leading-tight focus:outline-none focus:shadow-outline"
                id="password"
                type="password"
                placeholder="********"
                value={password}
                onChange={(e) => setPassword(e.target.value)}
              />
            </div>
            <div className="flex items-center justify-between">
              <button
                className="bg-blue-500 hover:bg-blue-700 text-white font-bold py-4 px-12 rounded focus:outline-none focus:shadow-outline"
                type="button"
                onClick={handleSubmit}
              >
                Sign Up
              </button>
              <a
                className="inline-block align-baseline font-bold text-sm text-blue-500 hover:text-blue-800"
                href="#"
              >
                Forgot Password?
              </a>
            </div>
          </form>
        </div>
      </div>
    </div>
  );
};

export default SignUp;

Installing necessary dependencies

We need to install the necessary dependencies:

yarn add axios

Now, if we visit http://localhost:3000/sign-up, we should see the following page:

Register page

If we fill in the details of the form, we can view the response from the server in the browser's console:

Create a new user

In the Strapi Admin Panel, we can see the new user:

Users list

Next, we need to save the token in a cookie. We'll be using a plugin nookies for handling that. So, let's install that dependency:

yarn add nookies

We need to update our handleSubmit method:

frontend/pages/sign-up.js
import React, { useState } from "react";
import Head from "next/head";
import axios from "axios";
import { setCookie } from "nookies";

  ..

const SignUp = () => {

  ..

  const handleSubmit = async e => {
    e.preventDefault();

    const res = await axios.post("http://localhost:1337/auth/local/register", {
      username,
      email,
      password
    });

    setCookie("", "token", res.data.jwt, {
      maxAge: 30 * 24 * 60 * 60,
      path: "/"
    });
  };

  ..

}

Now, if we try to register a new user, the token will be stored in the cookie:

Storing the token in the cookie

Setting up permissions for Products API

According to Strapi's Token Usage, we need to send the token in the Authorization header.

First, we need to allow authenticated users to view all the products. To do that, we need to give all the permissions to authenticated users:

Permissions for authenticated users

If we do GET http://localhost:1337/products, we'll get an error:

Error for non-authenticated users

We need to send the token in the Authorization header to get the proper data:

Successful response for authenticated users

Redirecting users to index page for authenticated users

Next, we'll redirect all the users to the index page if there is a token present and the user visited the sign up page:

frontend/pages/sign-up.js

SignUp.getInitialProps = (ctx) => {
  const isAuthenticated = !!parseCookies(ctx).token;

  // When the user is authenticated, don't let the user visit the
  // sign-in and sign-up routes
  if (isAuthenticated && ["/sign-up", "/sign-in"].indexOf(ctx.asPath) > -1) {
    if (typeof window !== "undefined") {
      Router.push("/");
    } else {
      if (ctx.res) {
        ctx.res.writeHead(301, {
          Location: "/",
        });
        ctx.res.end();
      }
    }
  }

  return {};
};

Adding the option to unauthenticate a user

We just need to add the option to log a user our. We'll add a button on the Nav component:

  ..

import { destroyCookie } from "nookies";
import Router from "next/router";

  ..

const handleSignOut = () => {
  destroyCookie("", "token");
  Router.push("/sign-up");
};

const Nav = () => (
  <nav>
    <ul>

      ..

      <li>
        <button onClick={handleSignOut}>Log out</button>
      </li>
    </ul>

  ..

The handleSignOut method will remove the token cookie and then redirect the user to the http://localhost:3000/sign-up route.

Conclusion

In this tutorial, we've learnt about how to perform authentication using Strapi and Next.js. You can refer to this commit for all the changes in this tutorial. I hope that this article helps you in your future projects.