Client-Side API Version Selection with Headers

// Function to make API requests with a specified version
async function callApi(url, version, options = {}) {
  const headers = {
    'Content-Type': 'application/json',
    ...options.headers
  };

  // Common patterns for API versioning via headers:

  // 1. Custom Header (e.g., X-API-Version)
  if (version) {
    headers['X-API-Version'] = version;
  }

  // 2. Accept Header (Vendor-specific media type)
  // e.g., 'Accept': 'application/vnd.myapi.v2+json'
  // if (version) {
  //   headers['Accept'] = `application/vnd.myapi.v${version}+json`;
  // }

  try {
    const response = await fetch(url, { ...options, headers });

    if (!response.ok) {
      const errorData = await response.json().catch(() => ({ message: response.statusText }));
      throw new Error(`API call failed (v${version}): ${response.status} - ${errorData.message}`);
    }

    return await response.json();
  } catch (error) {
    console.error(`Error calling API (v${version}):`, error);
    throw error;
  }
}

// --- Example Usage ---
// Assuming a hypothetical API that uses 'X-API-Version' header
// and returns different data structures or logic based on the version.

// (async () => {
//   try {
//     // Fetch data using API Version 1
//     console.log('Fetching data with API Version 1...');
//     const dataV1 = await callApi('/api/products', '1');
//     console.log('API V1 Response:', dataV1);
//     // Expected: { id: 'prod-abc', name: 'Widget', price: 29.99 }

//     // Fetch data using API Version 2 (might have different fields or formats)
//     console.log('
Fetching data with API Version 2...');
//     const dataV2 = await callApi('/api/products', '2');
//     console.log('API V2 Response:', dataV2);
//     // Expected: { product_id: 'prod-abc', product_name: 'Super Widget', current_price: 34.50, currency: 'USD' }

//     // Example with an API that doesn't exist, or a version not supported
//     console.log('
Fetching data with unsupported API Version...');
//     await callApi('/api/products', '99').catch(e => console.error('Caught error for V99:', e.message));

//   } catch (error) {
//     console.error('An unhandled error occurred:', error);
//   }
// })();

// --- Hypothetical Server-Side Endpoint (Node.js with Express) to demonstrate versioning ---
/*
const express = require('express');
const app = express();
const PORT = 3000;

app.get('/api/products', (req, res) => {
    const apiVersion = req.headers['x-api-version'] || '1'; // Default to V1

    if (apiVersion === '1') {
        res.json({ id: 'prod-abc', name: 'Widget', price: 29.99 });
    } else if (apiVersion === '2') {
        res.json({ product_id: 'prod-abc', product_name: 'Super Widget', current_price: 34.50, currency: 'USD' });
    } else {
        res.status(400).json({ error: `Unsupported API version: ${apiVersion}` });
    }
});

app.listen(PORT, () => console.log(`Server listening on port ${PORT}`));
*/