This story originally published on Geek Culture by me. This version is a mirror.

In this post, we will create a subscription form using Mailchimp API with a Next.js application handle by a custom Express server with Typescript support. The main purpose of this post is to show how all these technologies can be combined together to support this with a useful example. You can build whatever you want on this stack that we will build.

Table of Contents

  • Stack Introduction
  • Creating a Next.js Custom Express Server with TypeScript Configuration
  • Mailchimp API Integration and Creating Submit Form

1. Stack Introduction

Why Next.js?

1. Relatively easy to learn.

Next.js offers you advanced tools and a robust API support, but it doesn’t force you to use them.

2. Built-in CSS support.

Writing CSS in component-driven frameworks comes with a sacrosanct need for the “cascade”. It’s why you have CSS-in-JS tools, but Next.js comes out of the box with its own offering — styled-jsx, and also supports a bevy of styling methodologies.

3. Automatic TypeScript support.

If you like to code in TypeScript, with Next.js, you have the advantage of TypeScript being compiled and supported automatically for you.

4. Multiple data fetching technique.

It supports SSG and SSR. You can choose to use one or the other, or both.

4. Multiple data fetching technique.

It supports SSG and SSR. You can choose to use one or the other, or both.

5. File-system routing.

Navigating between one page to another is supported through the file-system of your app. You do not need any special library to handle routing.

Getting Started with Next.js

Why TypeScript?

Why You Should Choose TypeScript Over JavaScript

Why Custom Express Server?

Advanced Features: Custom Server

2. Creating our project

So, let’s get started! First of all, create an empty folder where you will install your project. Then go to the project directory and install all the following dependencies below.

npm init
npm install react react-dom next
npm install express
npm install --save-dev typescript @types/node @types/react
npm install --save-dev ts-node @types/express
npm fund

Project Structure

After dependency installation, create the following project structure in your directory. Later, we will update this structure according to our needs.

├─ server
│  └─ server.ts
├─ src
│  └─ pages
│     └─ home.tsx
├─ package.json
├─ tsconfig.json
└─ tsconfig.server.json

Put the following configuration files and entry point in the files you created.

// server.ts

import express, { Request, Response } from "express";
import next from "next";
const dev = process.env.NODE_ENV !== 'production';
const app = next({ dev });
const handle = app.getRequestHandler();
const port = process.env.PORT || 8080;
(async () => {
    try {
       await app.prepare();
       const server = express();
       server.all("*", (req: Request, res: Response) => {
         return handle(req, res);
       server.listen(port, (err?: any) => { 
         if (err) throw err;  
             console.log(`> Launched on http://localhost:${port}`);});
} catch (e) {

// index.ts

Now, create an index.tsx that is located in the src/pages directory. And put the following codes in index.tsx file.

function HomePage() {
  return <div> <h1>Hello World!</h1> </div>;
export default HomePage;

// package.json

Install the scripts below by editing the package.json file.

"scripts": {
  "dev": "ts-node --project tsconfig.server.json server/server.ts",
  "build:server": "tsc --project tsconfig.server.json",
  "build:next": "next build",
  "build": "npm run build:next && npm run build:server",
  "start": "NODE_ENV=production node dist/index.js"

Configuration Files

// tsconfig.json

  "compilerOptions": {
     "target": "es6",
     "lib": [
       "dom","dom.iterable", "esnext"],
     "allowJs": true,
     "skipLibCheck": true,
     "strict": false,
     "forceConsistentCasingInFileNames": true,
     "noEmit": true,
     "esModuleInterop": true,
     "module": "esnext",
     "moduleResolution": "node",
     "resolveJsonModule": true,
     "isolatedModules": true,
     "jsx": "preserve" },
     "exclude": [ "node_modules"],
     "include": [ "next-env.d.ts", "**/*.ts", "**/*.tsx"]}

// tsconfig.server.json

   "extends": "./tsconfig.json",  
   "compilerOptions": {    
   "module": "commonjs",
   "outDir": "dist",
   "noEmit": false  },
   "include": ["server"]

We are now ready to run Next.js on a TypeScript supported custom Express server. If you want to do something else, not the subscription form, you can use the structure we used so far.

3. Mailchimp Integration and Creating Submit Form

Before running our project, follow the steps below to integrate Mailchimp API.

// Updating structure


Adding src/pages/api/subscribe.ts

import axios from "axios"
function Req(email) {
// Creating API Key:
const API_KEY = "KEY HERE";
//Find your ID:
const url = `https://${DATACENTER}${AUDIENCE_ID}/members`
const data = {
  email_address: email,
  status: "subscribed",
const base64ApiKey = Buffer.from(`anystring:${API_KEY}`).toString("base64")
const headers = {
   "Content-Type": "application/json",
   Authorization: `Basic ${base64ApiKey}`,
return {
export default async (req, res) => {
   const { email } = req.body
   if (!email || !email.length) {
     return res.status(400).json({
       error: "Forgot to submit your email address?",
try {
   const { url, data, headers } = Req(email)
   const response = await, data, { headers })
   return res.status(201).json({ error: null })
} catch (error) {
  return res.status(400).json({
     error: `Please enter a valid email address.`,

// Updating our src/pages/index.tsx

import { useState } from 'react'
import axios from "axios"
export default function Home() {
   const [errorMessage, setErrorMessage] = useState(null)
   const [email, setEmail] = useState("")
   const [state, setState] = useState("IDLE")
const subscribe = async () => {
   try {
      const response = await"api/subscribe", { email })
   } catch (e) {
return (
      placeholder="Enter your email to subscribe"
      onChange={(e) => setEmail(}
    {state === "ERROR" && <p>{errorMessage}</p>}
      disabled={state === "LOADING"}
    {state === "SUCCESS" && <p><i>You have successfully registered on mailing list! 🎉</i></p>}


After our complete customization, run the npm run dev command and visit http://localhost:8080 to view our homepage.

Additional: Styling

If you want to add a style to the sample application we made, create a styles folder in the main directory of your project structure and add your CSS file. Then, import the CSS file you prepared into our index.tsx file and assign a class to the elements you want to style as follows.

// Import
import styles from '../../styles/Home.module.css'
// Example
    placeholder="Enter your email to subscribe"
    onChange={(e) => setEmail(}

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