Introduction

This blog post guides you through integrating the Mailchimp API into a Vite React application, a task crucial for automating your email marketing strategies.
Whether a simple email input or a comprehensive sign-up form, this guide is a baseline to tie into any event action, like a user clicking a form button.

const EmailForm = () => {
  const handleSubmit = (e) => {
    // ...
    subscribeUser(e.target.value) // mailchimp api call
  }
  // ...
  return (
    <EmailForm>
      {/* ... */}
      <button onclick={handleSubmit}>
        Subscribe
      </button>
    </EmailForm>
  )
}

Prerequisites

• Basic understanding of React, Node.js, and Vite
• Mailchimp account

Here’s a suggested folder layout for your application, separating the frontend (Vite React app) and backend (Node.js server):

/frontend
├── node_modules/
├── public/
│   └── index.html
├── src/
│   ├── components/        # React components
│   │   ├── App.jsx
│   │   └── EmailForm.jsx
│   └── ...
├── package.json
├── vite.config.js
└── ...
/backend
├── node_modules/
├── .env                   # Env variables for backend
├── package.json
├── server.js              # Main server file
└── ...

Step 1: Getting API Key and List ID from Mailchimp

NOTE: You can find this information in your Mailchimp account under Account Settings -> Extras -> API keys

• MAILCHIMP_API_KEY: Grants your application the necessary permissions to interact with your Mailchimp account
• MAILCHIMP_LIST_ID: Unique identifier for a specific audience (or list) in your Mailchimp account and determines where your data goes (which audience it affects)
• MAILCHIMP_SERVER_PREFIX: Refers to the subdomain part of the API endpoint URL. This subdomain is specific to your Mailchimp account and determines the data center where your account is hosted.

This is usually the suffix of your API Key or prefix of your API endpoint

Example: us20

Step 2: Setting Up the Backend

Create a separate Node.js project in the /backend directory

mkdir backend
cd backend
npm init -y
touch server.js

Install required packages:

npm install express @mailchimp/mailchimp_marketing dotenv cors

Step 3: Backend Code for Mailchimp Integration

Create an endpoint in your backend to handle the form submission. This endpoint will receive the user’s email from your front end and make an API call to Mailchimp.

const express = require('express');
const cors = require('cors');
require('dotenv').config();
const client = require("@mailchimp/mailchimp_marketing");
const app = express();

app.use(cors());
app.use(express.json());

client.setConfig({
  apiKey: process.env.MAILCHIMP_API_KEY,
  server: process.env.MAILCHIMP_SERVER_PREFIX,
});

app.post('/subscribe', async (req, res) => {
  const { email } = req.body;
  if (!email) {
    return res.status(400).send('Email is required');
  }
  try {
    const response = await client.lists.addListMember(process.env.MAILCHIMP_LIST_ID, {
      email_address: email,
      status: "pending", // or "subscribed" based on your preference
    });
    res.status(200).json(response);
  } catch (error) {
    console.error('Error with Mailchimp API:', error);
    res.status(500).json({ message: 'Internal Server Error', details: error.message });
  }
});

const PORT = process.env.PORT || 3001;
app.listen(PORT, () => console.log(`Server running on port ${PORT}`));

Step 4: Frontend Integration

NOTE: This guide is agnostic of your front-end implementation. The aim is solely to tie the form submission to a user action. Below is a straightforward method that can be attached to a component as an onClick event.

const subscribeUser = async (email) => {
  try {
    const response = await fetch("http://localhost:3001/subscribe", {
      method: "POST",
      body: JSON.stringify({ email }),
      headers: {
        "Content-Type": "application/json",
      },
    });
    // Handle response
  } catch (error) {
    console.error("Subscription error:", error);
  }
};

Install concurrently to run both servers at the same time:

npm install concurrently --save-dev

Adjust your package.json based on your project setup:

"scripts": {
  "start": "vite", // will run FE
  "dev": "concurrently \"npm run start\" \"cd backend && node server.js\"" // will run FE and BE
}

Step 5: Environment Variables Setup

API keys should always be safeguarded against unauthorized access and never embedded directly in your codebase. A .env file is used to store environment variables securely, in this case, your Mailchimp API key, Server Prefix, and List ID.

Example .env file configuration (Place this file in the root of your /backend directory):

MAILCHIMP_API_KEY=your_mailchimp_api_key_here
MAILCHIMP_SERVER_PREFIX=your_mailchimp_server_prefix_here
MAILCHIMP_LIST_ID=your_mailchimp_list_id_here
PORT=3001

Note: Always add .env to .gitignore to keep it out of version control.

Step 6: Testing and Debugging

Based on our setup in step 4, run npm run dev in /frontend to start your servers.

Debugging common errors and things to double-check:

• Verify that your List ID and data center prefix are correct.
• Review the Mailchimp API documentation to ensure you use the correct endpoint and URL format.
• Check the API key and ensure it’s correctly set up in your .env file.
• Ensure proper network connectivity to reach Mailchimp’s API servers.
• Verify if any firewall or security settings on your server might be blocking outbound HTTP requests.

Common Errors and Solutions

• Module Not Found Error: Refer back to Step 2 and ensure all backend resources are correctly installed
• 404 Error: Resource Not Found: Check the latest documentation to diagnose endpoint issues, ensure consistency of ports between frontend and backend
• 401 Error: API Key Invalid: Ensure that the API key is valid and stored correctly in backend/.env

Conclusion

Our focus here is on the backend setup and front-end integration, irrespective of how your subscription form is implemented. Feel free to tweak as needed.

Happy coding and marketing!

Additional Resources

• Mailchimp API Documentation