Node.js — Transform Stream: Split Chunks into Lines

readline did the line splitting for you. Time to write it: a
[`Transform`](https://nodejs.org/api/stream.html#class-streamtransform) stream receives byte
chunks on one side and pushes lines on the other. tinyserve will use it to process request
bodies and logs as they arrive.

Your task

Complete class LineSplitter extends Transform. Its readable side is in object mode: each
this.push(line) emits one string.

• Lines are separated by \n; a \r just before it (or at the very end) is removed.
• Empty lines are emitted as ''. The text after the last \n, if any, is emitted when the

input ends — in _flush(callback).

• Chunks are cut anywhere: in the middle of a line, between \r and \n, or inside a

multi-byte UTF-8 character.

The driver cuts the UTF-8 bytes of each test's text at the given byte offsets and pipes the
pieces through your splitter.

The multi-byte trap

é is two bytes (c3 a9). If one chunk ends with c3, chunk.toString() produces �
— the character is lost. A
[`StringDecoder`](https://nodejs.org/api/string_decoder.html) keeps incomplete characters
until the next write(), and end() returns what is left.

// text 'café\nthé\n' cut at byte 4 → chunks 'caf\xc3' and '\xa9\nthé\n'
// → ['café', 'thé']