read-next-line

Is s a lightweight, efficient utility for reading lines from a ReadableStream in JavaScript. The primary goal of this module is to enable memory-efficient line-by-line processing of large data streams, such as logs, files, or real-time data feeds.

Features

• Line-based processing: Reads lines directly from any ReadableStream.

• Memory efficiency: Keeps memory usage low by processing one line at a time.

• Browser compatibility: Works seamlessly with modern web browsers.

• Node.js compatibility: Works seamlessly with Node.js Web Streams API.

• Supports the following text encoding:

  • UTF-8 (default)
  • UTF-8 with the BOM field set
  • UTF-16LE with the BOM field is set
  • UTF-16BE with the BOM field is set

• Supports different line endings:

  Type	Abbreviation	Escape sequence
  Windows	CR LF	\r\n
  Unix	LF	\n
  Acorn BBC / RISC OS	LF CR	\n\r
  classic Mac OS	CR	\r

Installation

Install the package via npm:

1npm install read-next-line

Compatibility

read-next-line is a hybrid JavaScript module, supporting:

• ECMAScript Module (ESM)
• CommonJS backwards compatibility support

Designed to work with Works seamlessly with either:

• Node.js Readable streams
• Node.js Web Streams API
• Streams-API in the browser

Compatible with modern web browsers or Node.js ≥ 18.

Usage

Import and use StreamLineReader in your project:

In ESM projects or any TypeScript project use:

1import {ReadNextLine} from 'read-next-line';

In CommonJS projects use:

1const {ReadNextLine} = require('read-next-line');

Using read-next-line to read lines of text of a binary ReadableStream or Node.js Readable streams:

1async function processStream(stream) {
2	const reader = new ReadNextLine(stream);
3
4	let line;
5	while ((line = await reader.readLine()) !== null) {
6		console.log(line); // Process each line as needed
7	}
8}

You may as well use the LineSplitter which is a TransformStream<Uint8Array, string>, converting a binary stream into stream of lines (strings).

1import {LineSplitter} from 'read-next-line';
2
3const lineStream = webStream.pipeThrough(lineSplitter);
4const lineReader = lineStream.getReader();

Parsing a Blob/File

To process a file input, wrap the file's stream with ReadNextLine:

1async function proccessTextFile(blob) {
2	const reader = new ReadNextLine(blob.stream());
3	try {
4		let line;
5		do {
6			line = await reader.readLine();
7			console.log(line);
8		}
9		while (line !== null);
10	} finally {
11		reader.release();
12	}
13}
14const file = document.querySelector('#fileInput').files[0];
15proccessTextFile(file);

Online example can be found here: https://playcode.io/2226348

API

StreamLineReader Class

Constructor

1new StreamLineReader(stream: ReadableStream<Uint8Array>);

• stream: The ReadableStream to process.

Methods

• readLine(): Promise<string | null>
  • Reads the next line from the stream. Returns null if the stream ends.
• release(): void
  • Release the internal Reader.

License

This project is licensed under the MIT License. Feel free to use, modify, and distribute as needed.