JSON Lint

A JSON parser and validator with a command-line client. A pure JavaScript version of the service provided at jsonlint.com.

This is a fork of the original package with the following extensions:

• Handles multiple files on the command line (by Greg Inman).
• Walks directories recursively (by Paul Vollmer).
• Supports JSON schema drafts 04, 06 and 07.
• Can parse and skip JavaScript-style comments.
• Can accept single quotes (apostrophes) as string delimiters.
• Depends on up-to-date npm modules with no installation warnings.

Command-line Interface

Install jsonlint with `npm`` globally to be able to use the command-line interface:

npm i @prantlf/jsonlint -g

Validate a file like so:

jsonlint myfile.json

or pipe the input into stdin:

cat myfile.json | jsonlint

or process all .json files in a directory:

jsonlint mydir

jsonlint will either report a syntax error with details or pretty print the source if it is valid.

Options

$ jsonlint -h

Usage: jsonlint [options] [<file or directory> ...]

JSON parser and validator - checks syntax and semantics of JSON data.

Options:
  -s, --sort-keys              sort object keys
  -E, --extensions [ext]       file extensions to process for directory walk
                               (default: ["json","JSON"])
  -i, --in-place               overwrite the input files
  -t, --indent [char]          characters to use for indentation (default: "  ")
  -c, --compact                compact error display
  -C, --comments               recognize and ignore JavaScript-style comments
  -S, --single-quoted-strings  support single quotes as string delimiters
  -V, --validate [file]        JSON schema file to use for validation
  -e, --environment [env]      which specification of JSON Schema the validation
                               file uses (default: "json-schema-draft-03")
  -q, --quiet                  do not print the parsed json to stdin
  -p, --pretty-print           force pretty-printing even for invalid input
  -v, --version                output the version number
  -h, --help                   output usage information

If no files or directories are specified, stdin will be parsed. Environments
for JSON schema validation are "json-schema-draft-04", "json-schema-draft-06"
or "json-schema-draft-07".

Module Interface

Install jsonlint with npm locally to be able to use the module programmatically:

npm i @prantlf/jsonlint -D

You might prefer methods this module to the built-in JSON.parse method because of a better error reporting or support for JavaScript-like comments:

const { parser } = require('jsonlint')
// Fails at the position of the character "?".
parser.parse('{"creative": ?}') // throws an error
// Succeeds returning the parsed JSON object.
parser.parseWithComments('{"creative": false /* for creativity */}')
// Accepts parameters ignoreComments and allowSingleQuotedStrings.
parser.parse('{\'creative\': false}', { allowSingleQuotedStrings: true })

Parsing methods return the parsed object or throw an Error. If the data cam be parsed, you will be able to validate them against a JSON schema:

const { parser } = require('jsonlint')
const validator = require('jsonlint/lib/validator')
const validate = validator.compile('string with JSON schema')
validate(parser.parse('string with JSON data'))

Performance

These are the results of parsing a 2.2 KB formatted string (package.json) with Node.js 10.15.3:

the built-in parser x 112,338 ops/sec ±1.09% (89 runs sampled)
the custom parser x 3,520 ops/sec ±1.42% (88 runs sampled)
the parser with comment recognition x 3,406 ops/sec ±1.18% (87 runs sampled)

The custom pure-JavaScript parser is a lot slower than the built-in one. However, it is more important to have a clear error reporting than the highest speed in scenarios like parsing configuration files.

License

Copyright (C) 2012-2019 Zachary Carter, Ferdinand Prantl

Licensed under the MIT license.