Unhandled Promise Rejections & Uncaught Exceptions.

In Simple Words:

• process.on('uncaughtException', (err) => ...): Synchronous uncaught error. The application is in an undefined state and must perform cleanup and exit with non-zero code.
• process.on('unhandledRejection', (reason, promise) => ...): Promise rejected without a .catch(). In modern Node.js, terminates the process if unhandled.

process.on('uncaughtException', (err) => {
  console.error('Fatal synchronous exception:', err);
  // Perform minimal synchronous logging and exit:
  process.exit(1);
});

process.on('unhandledRejection', (reason) => {
  console.error('Unhandled Promise Rejection:', reason);
});