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vfile utility to create a report in machine readable JSON.


What is this?

This package is like vfile-reporter but it outputs machine readable JSON.

When should I use this?

You can use this when you need to serialize lint results for machines, use vfile-reporter itself for humans.


This package is ESM only. In Node.js (version 16+), install with npm:

npm install vfile-reporter-json

In Deno with esm.sh:

import {reporterJson} from 'https://esm.sh/vfile-reporter-json@4'

In browsers with esm.sh:

<script type="module">
  import {reporterJson} from 'https://esm.sh/vfile-reporter-json@4?bundle'


import {VFile} from 'vfile'
import {reporterJson} from 'vfile-reporter-json'

const one = new VFile({path: 'test/fixture/1.js'})
const two = new VFile({path: 'test/fixture/2.js'})

one.message('Warning!', {line: 2, column: 4})

console.log(reporterJson([one, two]))




This package exports the identifier reporterJson. That identifier is also the default export.

reporterJson(files[, options])

Create a serialized JSON report from one file or multiple files.

  • files (Array<VFile> or VFile) — file or files to report
  • options (Options, default: {}) — configuration

Report as serialized JSON (string).

Reporters must return strings, which is why serialized JSON is exposed. You can parse the result with JSON.parse, in which case you will get Array<JsonFile>.


JSON file (TypeScript type).

  • cwd (string) — base of path
  • history (Array<string>) — list of filepaths the file moved between; the first is the original path and the last is the current path
  • messages (Array<JsonMessage>) — list of filepaths the file moved between; the first is the original path and the last is the current path
  • path (string) — full path (example: '~/index.min.js')


JSON message (TypeScript type).

  • ancestors (Array<Node> or undefined) — stack of ancestor nodes surrounding the message
  • column (number or undefined) — starting column of message
  • fatal (boolean or undefined) — state of problem; true: error, file not usable; false: warning, change may be needed; undefined: change likely not needed
  • line (number or undefined) — starting line of message
  • place (Point, Position, or undefined) — place of message
  • reason (string) — reason for message, should use markdown
  • ruleId (string | null) — category of message (example: 'my-rule')
  • source (string | null) — namespace of message (example: 'my-package')
  • actual (string | null | undefined) — specify the source value that’s being reported, which is deemed incorrect
  • expected (Array<string> | null | undefined) — suggest acceptable values that can be used instead of actual
  • note (string | null | undefined) — long form description of the message, should use markdown
  • url (string | null | undefined) — link to docs for the message; this must be an absolute URL that can be passed as x to new URL(x)


Configuration (TypeScript type).

  • pretty (boolean, number, or string, default: 0) — value of space of JSON.stringify(x, undefined, space)
  • quiet (boolean, default: false) — do not show files without messages
  • silent (boolean, default: false) — show errors only; this does not show info and warning messages; also sets quiet to true


This package is fully typed with TypeScript. It exports the additional types JsonFile, JsonMessage, and Options.


Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, vfile-reporter-json@^4, compatible with Node.js 16.


See contributing.md in vfile/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.


MIT © Titus Wormer

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