@tabnas/jsonc

A JSONC (JSON-with-comments) grammar plugin for the tabnas parser. It teaches the jsonic relaxed-JSON grammar to parse JSONC: standard JSON plus single-line (//) and block (/* */) comments, with optional trailing commas.

| | This open source module is sponsored and supported by Voxgig. | | ---------------------------------------------------- | --------------------------------------------------------------------------------------- |

Install

@tabnas/jsonc is a plugin; install it alongside the engine and the base grammar:

npm install @tabnas/parser @tabnas/jsonic @tabnas/jsonc

Example

import { Tabnas } from '@tabnas/parser'
import { jsonic } from '@tabnas/jsonic'
import { Jsonc } from '@tabnas/jsonc'

const j = new Tabnas().use(jsonic).use(Jsonc)

j.parse('{ "name": "app", /* version */ "version": "1.0" }')
// => { name: 'app', version: '1.0' }

Enable trailing commas with an option at install time:

import { Tabnas } from '@tabnas/parser'
import { jsonic } from '@tabnas/jsonic'
import { Jsonc } from '@tabnas/jsonc'

const j = new Tabnas().use(jsonic).use(Jsonc, { allowTrailingComma: true })
j.parse('{ "debug": true, "verbose": false, }')
// => { debug: true, verbose: false }

Documentation

The docs follow the four Diátaxis quadrants:

• Tutorial — a guided first parse (learning).
• How-to guide — task recipes (install as a plugin, set options, handle errors, extend).
• Reference — the public API, every option, and the accepted syntax.
• Concepts — how the plugin works on the engine, and why.

Grammar diagram

The installed grammar as a railroad/syntax diagram, generated from the live grammar with @tabnas/railroad:

ASCII version: doc/grammar.txt. The grammar is defined in the repository-root jsonc-grammar.jsonic and embedded into src/jsonc.ts (and the Go port) via embed-grammar.js.

Acknowledgments

Conformance testing uses third-party corpora under MIT License:

• nst/JSONTestSuite by Nicolas Seriot — vendored at test/JSONTestSuite/.
• microsoft/node-jsonc-parser — parse-level test cases ported into test/jsonc.test.ts.

See THIRD_PARTY_NOTICES.md for details.

License

MIT. Copyright (c) 2021-2025 Richard Rodger and contributors.