Create a Node.js Proxy for External APIs to Bypass CORS

// server.js
const express = require('express');
const axios = require('axios');
const cors = require('cors'); // Required for allowing frontend to talk to this proxy

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

// Enable CORS for all origins, or specify allowed origins for production
app.use(cors());

// Middleware to parse JSON bodies
app.use(express.json());
app.use(express.urlencoded({ extended: true }));

// Define a proxy endpoint
app.all('/proxy/:apiName/*', async (req, res) => {
  // In a real application, you would configure actual external API bases
  // based on `apiName` or other indicators. For example:
  // const apiMap = { 
  //   'github': 'https://api.github.com',
  //   'weather': 'https://api.openweathermap.org/data/2.5'
  // };
  // const externalApiBase = apiMap[req.params.apiName];
  // if (!externalApiBase) { return res.status(404).send('API not found'); }

  // For this example, let's assume a single external API endpoint for simplicity.
  const externalApiBase = 'https://jsonplaceholder.typicode.com'; // Example external API

  const path = req.params[0]; // The rest of the path after /proxy/:apiName/
  const externalUrl = `${externalApiBase}/${path || ''}`;

  console.log(`Proxying ${req.method} request to: ${externalUrl}`);

  try {
    const config = {
      method: req.method,
      url: externalUrl,
      headers: {
        // Forward relevant headers, or add new ones
        'Content-Type': req.headers['content-type'] || 'application/json',
        // Example: 'Authorization': `Bearer ${process.env.EXTERNAL_API_TOKEN}`
      },
      params: req.query, // Forward query parameters
      data: req.body, // Forward request body for POST, PUT, PATCH
    };

    const apiResponse = await axios(config);

    // Forward the external API's response status and data to the client
    res.status(apiResponse.status).send(apiResponse.data);

  } catch (error) {
    console.error(`Proxy error for ${externalUrl}:`, error.message);
    if (error.response) {
      res.status(error.response.status).send(error.response.data);
    } else if (error.request) {
      res.status(503).send({ message: 'No response from external API.' });
    } else {
      res.status(500).send({ message: 'Internal proxy error.' });
    }
  }
});

app.get('/', (req, res) => {
    res.send('Node.js API Proxy is running. Use /proxy/:apiName/* to access external APIs.');
});

app.listen(PORT, () => {
  console.log(`Proxy server listening on port ${PORT}`);
  console.log(`To run: npm init -y && npm install express axios cors && node server.js`);
  console.log(`Example client-side usage: fetch('http://localhost:${PORT}/proxy/todos/1')`);
});