JSONC

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A small and fast JSONC parser. It just removes comments and then delegates parsing to the native JSON.parse implementation.

Features

• Uses native JSON.parse, including its optional reviver.
• Preserves exact source positions for parse errors.
• Can strip comments from JSON strings.
• Has no runtime dependencies.

Apart from comments, the input must be strict JSON. In particular, trailing commas are not accepted.

Installation

npm install @kayahr/jsonc

Parsing JSONC

Use JSONC.parse like JSON.parse:

import { JSONC } from "@kayahr/jsonc";

const config = JSONC.parse(`{
    // Server configuration
    "host": "localhost",
    "port": 8080
}`);

The optional reviver is passed directly to JSON.parse:

const config = JSONC.parse(source, (key, value) => key === "port" ? Number(value) : value);

Before parsing, every comment character is replaced with whitespace while CR and LF characters are retained. The resulting string therefore has the same length and line-break positions as the input, so positions reported by JSON.parse point into the original JSONC source.

Stripping comments

JSONC.strip returns strict JSON without parsing it. It uses "clean" mode by default:

const jsonString = JSONC.strip(`{
    // Server configuration
    "host": "localhost", // Interface
    "port": 8080
}`);

The result keeps the surrounding formatting and removes standalone comment lines:

{
    "host": "localhost",
    "port": 8080
}

Pass "preserve" when exact source offsets matter:

const jsonString = JSONC.strip(source, "preserve");

In "preserve" mode, comment characters become spaces and all CR and LF characters stay at their original offsets. JSONC.parse always uses this mode internally.

JSONC.strip is a lexical transformation and does not validate the result. Use JSONC.parse or JSON.parse when validation is required.