Introduction to Handling Files & Data in Node.js

In Node.js, most useful programs don't just compute values — they move data: from files to memory, from memory to the terminal, from one format to another, and sometimes from one process to the next.

To do that reliably, you need to understand the Node.js I/O toolbox: the fs module for files and directories, EventEmitter for asynchronous events, Buffer for raw bytes, and streams for processing data efficiently without loading everything at once.

These building blocks are commonly used to:

• Build real CLI utilities that inspect, transform, and generate files.
• Process large inputs without blowing up memory.
• Create pipelines that connect data sources to outputs.
• Handle interactive programs that read from stdin and write to stdout/stderr.
• Work closer to the "wire format" of data when needed (bytes and buffers).

This module is a turning point: once you're comfortable with files, buffers, and streams, you can build tools that feel like native Unix commands — fast, composable, and designed for real-world data.

Learning objectives

After completing this module, you will be able to:

• Read, write, copy, and remove files using the fs module.
• Create, read, copy, and remove directories programmatically.
• Emit and handle asynchronous events using EventEmitter.
• Work with bytes using Buffer to inspect and manipulate raw data.
• Process large files efficiently using readable and writable streams.
• Read from stdin and write to stdout and stderr to build interactive programs.
• Chain and transform streams to create data pipelines.