@asymmetric-effort/jsonlint

A pure TypeScript JSON parser, linter, and validator with detailed error reporting. Zero runtime dependencies.

Feature-compatible with zaach/jsonlint.

Installation

NPM Package

npm install @asymmetric-effort/jsonlint

Global CLI

npm install -g @asymmetric-effort/jsonlint

Standalone Binary

Pre-compiled standalone binaries are produced via make build. The binary requires no runtime dependencies.

CLI Usage

jsonlint myfile.json

Or pipe JSON via stdin:

echo '{"key": "value"}' | jsonlint

Options

| Flag | Long Form | Description | Default | |------|-----------|-------------|---------| | -v | --version | Print version and exit | | | -s | --sort-keys | Sort object keys in output | false | | -i | --in-place | Overwrite the input file with formatted output | false | | -t CHAR | --indent CHAR | Character(s) to use for indentation | " " (2 spaces) | | -c | --compact | Compact error display | false | | -V FILE | --validate FILE | Validate against a JSON Schema (Draft-03) file | | | -e ENV | --environment ENV | JSON Schema spec version | json-schema-draft-03 | | -q | --quiet | Do not print parsed JSON to stdout | false | | -p | --pretty-print | Force pretty printing even if invalid | false | | -h | --help | Show help message | |

Examples

Validate and pretty-print:

jsonlint data.json

Sort keys:

jsonlint -s data.json

Format in place:

jsonlint -i data.json

Validate against a schema:

jsonlint -V schema.json data.json

Compact errors (useful for editor integrations):

jsonlint -c data.json

Module API

import { parse } from "@asymmetric-effort/jsonlint";

// Returns parsed value or throws ParseError
const result = parse('{"key": "value"}');

Advanced Usage

import { JsonParser, ParseError, LexerError } from "@asymmetric-effort/jsonlint";

const parser = new JsonParser();

// Custom error handler
parser.parseError = (message, hash) => {
  console.error(`Error at line ${hash.line}: ${message}`);
  throw new ParseError(message, hash);
};

try {
  parser.parse(input);
} catch (e) {
  if (e instanceof ParseError) {
    console.error("Parse error:", e.hash);
  } else if (e instanceof LexerError) {
    console.error("Lexer error:", e.message);
  }
}

Formatter

import { formatJson } from "@asymmetric-effort/jsonlint";

// Best-effort formatting (works even on invalid JSON)
const formatted = formatJson('{"a":1,"b":2}', "  ");

Schema Validator

import { SchemaValidator } from "@asymmetric-effort/jsonlint";
import type { JsonSchema } from "@asymmetric-effort/jsonlint";

const schema: JsonSchema = {
  type: "object",
  properties: {
    name: { type: "string", required: true },
    age: { type: "integer", minimum: 0 },
  },
};

const validator = new SchemaValidator();
const errors = validator.validate({ name: "Alice", age: 30 }, schema);

if (errors.length > 0) {
  errors.forEach((e) => console.error(`${e.property}: ${e.message}`));
}

Building

make setup    # Install dependencies
make build    # Build library and standalone binary
make test     # Run all tests
make lint     # Run type checker
make help     # Show all targets

License

MIT License. Copyright (c) 2026 Asymmetric Effort, LLC.