@yukiakai/json-stream-parser

A lightweight and zero-dependency streaming JSON parser for Node.js and browsers.
It handles fragmented JSON input — such as from sockets, WebSockets, or chunked streams — and emits complete JSON values when they are fully parsed.

Features

• Parses streamed JSON incrementally (like from .write() chunks)
• Emits complete JSON values when available
• Detects incomplete vs. invalid JSON properly
• Skips strings "..." correctly to avoid false { or } detection
• Tiny and dependency-free

Installation

npm install @yukiakai/json-stream-parser

Usage

import { JsonStreamParser } from '@yukiakai/json-stream-parser';

const parser = new JsonStreamParser();

parser.on('data', (jsonValue) => {
  console.log('Parsed:', jsonValue);
});

parser.on('error', (err) => {
  console.error('Invalid JSON:', err.message);
});

// Simulate fragmented incoming JSON
parser.write('{"id":1,');
parser.write('"name":"Alice"}');
parser.write('\n{"id":2,"name":"B');
parser.write('ob"}');

API

new JsonStreamParser()

Creates a new instance of the streaming parser.

parser.write(chunk: string | Buffer)

Feeds partial input into the parser. It automatically buffers and emits full JSON values when complete.

Events

• data: (value: any) – Emitted when a full valid JSON value is parsed.
• error: (error: Error) – Emitted if an invalid JSON structure is detected (e.g. unclosed brace).

Example: With Socket

import net from 'net';
import { JsonStreamParser } from '@yukiakai/json-stream-parser';

const server = net.createServer((socket) => {
  const parser = new JsonStreamParser();

  parser.on('data', (obj) => {
    console.log('Received JSON:', obj);
  });

  parser.on('error', (err) => {
    console.warn('Bad JSON:', err.message);
    socket.destroy(); // or handle gracefully
  });

  socket.on('data', (chunk) => {
    parser.write(chunk);
  });
});

server.listen(3000);

Tests

npm run test

License

MIT © Yuki Akai