Node Callback Concept

In Node.js, callbacks enable asynchronous, non-blocking execution, while methods like readFileSync() perform blocking operations. The fs module provides both synchronous and asynchronous approaches to handle file system tasks.

• Callback Function: Executes after a task completes, enabling non-blocking processing.
• Improves Scalability: Allows handling multiple requests without waiting for operations to finish.
• readFileSync(): A synchronous method that blocks execution until the file is fully read.
• Asynchronous Methods: Continue execution while file operations run in the background.

Example: Code for reading a file synchronously (blocking code) in Nodejs. Create a text file inputfile1.txt with the following content:

Hello Programmer!!!
Learn NodeJS with GeeksforGeeks

Output:

👁 Image

• The fs library is used to perform file system operations in Node.js.
• The asynchronous readFile() function allows the program to continue execution while the file is being read in the background.
• A callback function is executed after the file-reading operation is completed.

Example : Code for reading a file asynchronously (non-blocking code) in Nodejs. Create a text file inputfile1.txt with the following content.

Hello Programmer!!!
Learn NodeJS with GeeksforGeeks

Output:

• The fs.readFile() function reads the file asynchronously (non-blocking).
• The program does not wait for the file to be read.
• "End of Program execution" is printed first.
• The file content is printed later when the callback runs.