In this Node.js tutorial for 2025, you will learn how to read a file line by line in Node.js efficiently. This method is especially useful when working with large text files, log files, CSV data, or datasets where loading the entire file into memory at once is not practical. By processing files line by line, you can build applications that are more memory-efficient, faster, and capable of handling huge data streams without slowing down.

Node.js provides multiple ways to read files, but when you need to process data incrementally, the best approach is to use its built-in fs module together with readline. This allows you to read the file stream in smaller chunks and handle each line as soon as it is available, rather than waiting for the whole file to load.

What You Will Learn in This Tutorial

Why reading files line by line is better for large datasets

How the fs module streams file data

Using the readline interface to process each line individually

Handling asynchronous file reading for maximum performance

Managing file read events to detect when processing is complete

Best practices to handle unexpected data formats

Using error handling to manage file access issues or invalid content

Working with different file encodings when reading text data

Real-World Use Cases

Reading and analyzing large log files without exhausting memory

Importing massive CSV files into a database one record at a time

Processing server access logs for analytics and monitoring

Handling streaming data from text-based sensors or IoT devices

Filtering specific lines from a dataset without loading the whole file

Best Practices You Will Learn

Always close file streams after reading to avoid memory leaks

Validate line content before processing to prevent errors

Handle encoding properly to avoid misreading special characters

Use asynchronous methods to keep the Node.js event loop free

Log file reading progress for better debugging and tracking

By the end of this tutorial, you will be able to read a file line by line in Node.js confidently, using efficient memory management and asynchronous processing. You will also understand how to integrate this technique into real-world applications such as analytics dashboards, data processing pipelines, and system monitoring tools.

This tutorial is part of the Node.js 2025 Playlist, which covers essential backend skills such as creating files, appending data, monitoring file changes, moving and renaming files, and advanced file handling techniques. Mastering line-by-line file reading will give you more control and scalability in your Node.js applications.

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