Authenticating API Requests with an API Key

const API_BASE_URL = 'https://api.example.com'; // Replace with your API base URL
const API_KEY = 'YOUR_SECRET_API_KEY'; // IMPORTANT: For client-side, consider environmental variables or server-side proxy

// Method 1: API Key in Request Header (most common and recommended)
async function fetchDataWithApiKeyHeader(endpoint, options = {}) {
    const headers = {
        'Content-Type': 'application/json',
        'Authorization': `ApiKey ${API_KEY}`, // Or `X-API-Key`, depends on API
        ...options.headers
    };
    const response = await fetch(`${API_BASE_URL}/${endpoint}`, { ...options, headers });
    if (!response.ok) {
        throw new Error(`API error: ${response.status} ${response.statusText}`);
    }
    return await response.json();
}

// Method 2: API Key as a Query Parameter (less secure, but sometimes required)
async function fetchDataWithApiKeyQuery(endpoint, options = {}) {
    const url = new URL(`${API_BASE_URL}/${endpoint}`);
    url.searchParams.append('apiKey', API_KEY); // 'apiKey' can vary
    // Merge existing query parameters from options.params if needed
    if (options.params) {
        Object.keys(options.params).forEach(key => url.searchParams.append(key, options.params[key]));
    }

    const response = await fetch(url.toString(), options);
    if (!response.ok) {
        throw new Error(`API error: ${response.status} ${response.statusText}`);
    }
    return await response.json();
}

// Usage Example:
/*
(async () => {
    try {
        // Replace with actual API endpoint that uses API Key auth
        // For demonstration, using a placeholder endpoint
        // const headerAuthData = await fetchDataWithApiKeyHeader('secure-data');
        // console.log('Data with header API key:', headerAuthData);

        // const queryAuthData = await fetchDataWithApiKeyQuery('public-data', { params: { user_id: 123 } });
        // console.log('Data with query API key:', queryAuthData);

        console.log("To run, replace API_BASE_URL and API_KEY, and uncomment usage examples.");
    } catch (err) {
        console.error('API Key auth failed:', err.message);
    }
})();
*/