Stream. Transform string chunks to data chunks.

LineStream.js

class LineStream extends Transform {
  constructor(...args) {
    super(...args);

    this.buffer = '';
  }

  _transform(chunk, encoding, callback) {
    const lines = chunk.toString().split('\n');
    lines[0] = this.buffer + lines[0];

    this.buffer = lines.length > 1 ?
      lines[lines.length - 1] :
      '';

    lines.forEach(l => this.push(l));
    callback();
  }
}