i-json

Strict JSON parser, serializer and validator conforming to I-JSON (RFC 7493).

What I-JSON requires

I-JSON is a restricted profile of JSON (RFC 8259) designed for interoperability. An I-JSON message must:

• be encoded in UTF-8
• contain no unpaired surrogates or noncharacters in strings, including when escaped ("\uDEAD")
• have no duplicate member names within an object
• use only numbers representable as IEEE 754 double-precision values (integers should be within ±(2^53 − 1))

Install

npm install @nozomi-hiragi/i-json

Also on JSR for Deno and other runtimes:

deno add jsr:@nozomi-hiragi/i-json
# or: npx jsr add @nozomi-hiragi/i-json

Usage

import { isIJson, parse, stringify, IJsonError } from "@nozomi-hiragi/i-json";

isIJson('{"a":1}'); // true
isIJson('{"a":1,"a":2}'); // false: duplicate member name

parse('{"name":"i-json"}'); // { name: "i-json" }
parse(new Uint8Array(bytes)); // UTF-8 bytes are validated too

try {
  parse('["\\uDEAD"]');
} catch (error) {
  if (error instanceof IJsonError) {
    error.rule; // "characters"
    error.position; // 2 (index of the escape)
  }
}

stringify({ a: [1, "x"] }); // '{"a":[1,"x"]}'
stringify({ a: undefined }); // throws IJsonError instead of dropping the member

parse and isIJson accept a string or UTF-8 bytes. stringify throws on anything JSON.stringify would silently drop or change: undefined, functions, symbols (as values or keys), bigints, NaN and Infinity, cycles, array holes and non-index array properties, non-plain objects (objects with toJSON are allowed), and strings with unpaired surrogates or noncharacters.

Options

| Option | Default | Effect | | --- | --- | --- | | strict | false | Also enforce the RFC 7493 SHOULD rules: a number must be written with the same value as the shortest representation of the double it parses to (no overflow, underflow, excess digits, or integer literals beyond ±(2^53−1)), and the top-level value must be an object or array. | | maxDepth | 512 | Maximum nesting of arrays and objects. |

By default only the MUST rules are enforced, since a message that breaks a SHOULD rule is still I-JSON. See docs/test-cases.md for every rule and decision.

License

MIT