Which operations and functions are synchronous in the code?

Synchronous operations block the thread until they complete.

Examples of synchronous operations in Node.js:

• File system operations ending with Sync:

  const fs = require('fs');
  
  // Synchronous file read
  const data = fs.readFileSync('file.txt', 'utf8');
  

• CPU-intensive blocking functions in modules that do not use asynchronous APIs, e.g., complex mathematical calculations in a loop.
• Certain native modules (C++) operations if not implemented asynchronously.
• Operations that are inherently blocking at the OS level, e.g., waiting for console input.

Most built-in Node.js functions that deal with network operations, file system, databases, etc., have asynchronous counterparts to avoid blocking the main thread. Synchronous versions are typically used only in command-line utilities or during initialization where blocking is acceptable.