Error Handling in Async Code

async function fetchUser(id) {
  try {
    const response = await fetch(`https://api.example.com/users/${id}`);
    if (!response.ok) {
      throw new Error(`HTTP ${response.status}: ${response.statusText}`);
    }
    const user = await response.json();
    return user;
  } catch (err) {
    // Network errors, JSON parse errors, HTTP errors all land here
    console.error("fetchUser failed:", err.message);
    throw err; // Re-throw so callers can handle it too
  }
}

process.on("unhandledRejection", function(reason, promise) {
  console.error("Unhandled Promise rejection:", reason);
  // In production, log to monitoring and exit cleanly
  process.exit(1);
});

process.on("uncaughtException", function(err) {
  console.error("Uncaught exception:", err);
  process.exit(1);
});

class AppError extends Error {
  constructor(message, statusCode = 500) {
    super(message);
    this.name = "AppError";
    this.statusCode = statusCode;
  }
}

async function getUser(id) {
  if (!id) throw new AppError("User ID is required", 400);
  // ...
}