json-seq-stream

application/json-seq / jsonl (NDJSON) support stream / async iterator library

This library provides composable TransformStream / ReadableWritablePair utilities to work with streaming JSON data formats.

Features

- [x] Supports RFC7464 (application/json-seq)
- [x] Supports JSON Lines / NDJSON (application/jsonl, application/x-ndjson)
- [x] Fully stream-compatible (Fetch API, File API, Bun/Deno, etc.)
- [x] Composable with standard Web Streams (pipeThrough())

---

Usage Examples

$3

``ts
import { InputJsonSequenceStream } from "json-seq-stream";

type Value = { value: number };

const sequenceStream = new InputJsonSequenceStream();

const response = await fetch(url);
const readable = response.body!.pipeThrough(sequenceStream);

for await (const value of readable) {
console.log(value);
}
`

JSON Lines / NDJSON

`ts
import { InputJsonLinesStream } from "json-seq-stream";

type Value = { value: number };

const linesStream = new InputJsonLinesStream();

const response = await fetch("https://example.com/data.jsonl");
const readable = response.body!.pipeThrough(linesStream);

for await (const value of readable) {
console.log(value);
}
`

Output Example

`ts
import { OutputJsonLinesStream } from "json-seq-stream";

type Value = { value: number };

const { readable, writable } = new OutputJsonLinesStream();

const writer = writable.getWriter();
writer.write({ value: 1 });
writer.write({ value: 2 });
writer.close();

for await (const chunk of readable) {
console.log(new TextDecoder().decode(chunk)); // NDJSON text lines
}
``

See also

- RFC 7464 - JavaScript Object Notation (JSON) Text Sequences \
https://datatracker.ietf.org/doc/html/rfc7464
- JSON Lines \
https://jsonlines.org
- JSON streaming - Wikipedia (en) \
https://en.wikipedia.org/wiki/JSON_streaming