Authenticating API Requests with Bearer Tokens in JavaScript

async function callAuthenticatedApi(url, token, method = 'GET', data = null) {
  const headers = {
    'Content-Type': 'application/json',
    'Authorization': `Bearer ${token}` // Include the Bearer token
  };

  const options = {
    method: method,
    headers: headers,
  };

  if (data && (method === 'POST' || method === 'PUT')) {
    options.body = JSON.stringify(data);
  }

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

    if (!response.ok) {
      // Handle specific authentication errors (e.g., 401 Unauthorized, 403 Forbidden)
      if (response.status === 401) {
        console.error("Authentication failed: Invalid or expired token.");
        // Optionally, redirect to login page or refresh token
      } else if (response.status === 403) {
        console.error("Authorization failed: Not permitted to access this resource.");
      }
      throw new Error(`HTTP error! Status: ${response.status}`);
    }

    const result = await response.json();
    return result;
  } catch (error)
  {
    console.error("Failed to call authenticated API:", error);
    throw error;
  }
}

// Example Usage:
// const MY_AUTH_TOKEN = 'your_actual_bearer_token_here'; // Get this from localStorage, sessionStorage, or state
// const PROTECTED_API_URL = 'https://api.example.com/protected-data';

// async function getProtectedData() {
//   if (!MY_AUTH_TOKEN) {
//     console.error("Auth token is missing. Please log in.");
//     return;
//   }
//   try {
//     const data = await callAuthenticatedApi(PROTECTED_API_URL, MY_AUTH_TOKEN);
//     console.log('Protected data:', data);
//   } catch (error) {
//     console.error('Failed to get protected data:', error);
//   }
// }

// getProtectedData();

// Example for POST with token:
// async function postProtectedData() {
//   if (!MY_AUTH_TOKEN) {
//     console.error("Auth token is missing. Please log in.");
//     return;
//   }
//   const postData = {
//     name: 'New Item',
//     value: 123
//   };
//   try {
//     const result = await callAuthenticatedApi(PROTECTED_API_URL, MY_AUTH_TOKEN, 'POST', postData);
//     console.log('Protected POST result:', result);
//   } catch (error) {
//     console.error('Failed to post protected data:', error);
//   }
// }
// postProtectedData();