What is split2?
The split2 npm package is a Node.js module that allows you to split a stream of text into lines, handling backpressure correctly. It's particularly useful for reading and processing large text files or logs line by line without loading the entire file into memory. This can significantly improve performance and efficiency when dealing with large datasets or streams.
What are split2's main functionalities?
Splitting a stream into lines
This feature allows you to read a file stream and split it into lines. Each line is then processed individually, which is useful for parsing logs or any line-based data.
"use strict";
const split2 = require('split2');
const fs = require('fs');
fs.createReadStream('file.txt')
.pipe(split2())
.on('data', function (line) {
console.log(line);
});
Using a custom matcher
This demonstrates how to use a custom regular expression as a matcher to split the stream. This is useful when lines are not just separated by a newline character but could include carriage returns or other variations.
"use strict";
const split2 = require('split2');
process.stdin
.pipe(split2(/(?:\r\n|\r|\n)/g))
.on('data', function (line) {
console.log('Line:', line);
});
Other packages similar to split2
byline
The byline package offers similar functionality to split2 by providing a simple way to read lines from a stream. However, it focuses more on simplicity and ease of use, potentially at the cost of some of the more advanced features and customizations offered by split2.
readline
While not an npm package but a core Node.js module, readline provides functionality to read data from a readable stream, such as the process.stdin, one line at a time. It's more complex and versatile than split2, offering more control over the input and output streams, but it might be overkill for simple line-splitting tasks.
through2
Though not exclusively for splitting streams into lines, through2 is a tiny wrapper around Node streams.Transform that makes it easier to create transform streams. It can be used in combination with other methods to achieve similar functionality to split2, offering a more flexible but potentially more complex solution.
Split2(matcher, mapper, options)
![build status](https://secure.travis-ci.org/mcollina/split2.png)
Break up a stream and reassemble it so that each line is a chunk.
split2
is inspired by @dominictarr split
module,
and it is totally API compatible with it.
However, it is based on through2
by @rvagg and it is fully based on Stream3.
matcher
may be a String
, or a RegExp
. Example, read every line in a file ...
fs.createReadStream(file)
.pipe(split2())
.on('data', function (line) {
})
split
takes the same arguments as string.split
except it defaults to '/\r?\n/' instead of ',', and the optional limit
paremeter is ignored.
String#split
split
takes an optional options object on it's third argument, which
is directly passed as a
Transform
option.
Calling .destroy
will make the stream emit close
. Use this to perform cleanup logic
var splitFile = function(filename) {
var file = fs.createReadStream(filename)
return file
.pipe(split2())
.on('close', function() {
file.destroy()
})
}
var stream = splitFile('my-file.txt')
stream.destroy()
NDJ - Newline Delimited Json
split2
accepts a function which transforms each line.
fs.createReadStream(file)
.pipe(split2(JSON.parse))
.on('data', function (obj) {
})
License
Copyright (c) 2014-2016, Matteo Collina hello@matteocollina.com
Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.