Splitly

Splits a stream on a new-line character and reassemble it into a stream of line-sized chunks. Zero dependencies with a focus on speed and simplicity.

There are a number of alternatives our there, namely split, binary-split and split2. All of which are significantly slower than this implementation and some have additional dependencies. Splitly extends stream.Duplex instead of stream.Transform for greater control over memory pressure and speed.

const splitly = require('splitly');

fs.createReadStream(file)
  .pipe(splitly.createStream())
  .on('data', function (line) {
    // each chunk is a separate line
    // chunks are buffers and are not stripped of the newline character(s)
    const trimmed = line.toString().trim();
  });

Note: Usage of the data event is not recommended in production code and should only be used for strictly synchronous/blocking code. Instead, pipe the output of the stream to another stream capable of propagating back pressure (such as process.stdout or a stream that writes to a database or makes an API call).

splitly requires the newline character(s) to be defined as a Buffer, unlike other split stream implementations which also accept regular expressions. Additionally, the newline character is not truncated from the chunk passed to the data event. The default newline character is \n. If you want to split on /\r?\n/ instead, keep the default newline character and trim() the chunk in the data callback.

API

createStream({ newlineChar: Buffer }, DuplexOptions )

• newlineChar <Buffer> Default: Buffer.from('\n')
• DuplexOptions <Object> Default: {} passed to stream.Duplex constructor

Custom Newline Character

const splitly = require('splitly');

const stream = splitly.createStream({
  // split on zero-byte delimited lines, must be provided as Buffer
  newlineChar: Buffer.from('\0'),
});

Benchmark

/dev/null is the raw performance of piping the test stream to /dev/null. This is the lower boundary of the performance that can be achieved. It also makes sure the file is in the OS file cache. See ./benchmark/index.js for details. Run under NodeJS v14.18.3.

name	time	stdev
/dev/null	5.41	2.67
splitly	10.35	4.91
split2	34.24	3.04
split	34.71	4.78
byline	39.55	13.72
binary-split	46.55	9.22