Simple API Proxy with Node.js/Express to Hide API Keys

// server.js (Node.js/Express)
const express = require('express');
const axios = require('axios');
const cors = require('cors'); // Required for cross-origin requests from frontend
require('dotenv').config(); // For loading environment variables

const app = express();
const PORT = process.env.PORT || 3001;

// Use CORS middleware if your frontend is on a different origin
app.use(cors());
app.use(express.json()); // For parsing application/json

// Example proxy for a third-party API that requires an API key
app.post('/api/external-data', async (req, res) => {
  const EXTERNAL_API_URL = 'https://external.api.com/data';
  const EXTERNAL_API_KEY = process.env.EXTERNAL_API_KEY; // Keep this secret!

  if (!EXTERNAL_API_KEY) {
    return res.status(500).json({ error: 'External API key not configured on server.' });
  }

  try {
    // Forward the request to the external API
    const externalApiResponse = await axios.post(EXTERNAL_API_URL, req.body, {
      headers: {
        'Authorization': `Bearer ${EXTERNAL_API_KEY}`, // Or 'x-api-key', etc.
        'Content-Type': 'application/json',
      },
    });
    res.status(externalApiResponse.status).json(externalApiResponse.data);
  } catch (error) {
    console.error('Proxy error:', error.response?.data || error.message);
    res.status(error.response?.status || 500).json({
      error: 'Failed to fetch data from external API',
      details: error.response?.data,
    });
  }
});

// Start the server
app.listen(PORT, () => {
  console.log(`Proxy server running on port ${PORT}`);
});

// To run this:
// 1. npm init -y
// 2. npm install express axios cors dotenv
// 3. Create a .env file: EXTERNAL_API_KEY=your_actual_secret_key
// 4. node server.js

// Frontend (example using fetch):
// async function fetchDataFromProxy() {
//   try {
//     const response = await fetch('http://localhost:3001/api/external-data', {
//       method: 'POST',
//       headers: {
//         'Content-Type': 'application/json',
//       },
//       body: JSON.stringify({ query: 'example' })
//     });
//     const data = await response.json();
//     console.log('Data from external API via proxy:', data);
//   } catch (error) {
//     console.error('Error fetching from proxy:', error);
//   }
// }
// fetchDataFromProxy();