Important: This documentation covers Yarn 1 (Classic).
For Yarn 2+ docs and migration guide, see yarnpkg.com.

Package detail

yargs-parser

yargs327.8mISC21.1.1TypeScript support: definitely-typed

the mighty option parser used by yargs

argument, parser, yargs, command, cli, parsing, option, args, argument

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yargs-parser

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The mighty option parser used by yargs.

visit the yargs website for more examples, and thorough usage instructions.

Example

npm i yargs-parser --save
const argv = require('yargs-parser')(process.argv.slice(2))
console.log(argv)
$ node example.js --foo=33 --bar hello
{ _: [], foo: 33, bar: 'hello' }

or parse a string!

const argv = require('yargs-parser')('--foo=99 --bar=33')
console.log(argv)
{ _: [], foo: 99, bar: 33 }

Convert an array of mixed types before passing to yargs-parser:

const parse = require('yargs-parser')
parse(['-f', 11, '--zoom', 55].join(' '))   // <-- array to string
parse(['-f', 11, '--zoom', 55].map(String)) // <-- array of strings

Deno Example

As of v19 yargs-parser supports Deno:

import parser from "https://deno.land/x/yargs_parser/deno.ts";

const argv = parser('--foo=99 --bar=9987930', {
  string: ['bar']
})
console.log(argv)

ESM Example

As of v19 yargs-parser supports ESM (both in Node.js and in the browser):

Node.js:

import parser from 'yargs-parser'

const argv = parser('--foo=99 --bar=9987930', {
  string: ['bar']
})
console.log(argv)

Browsers:

<!doctype html>
<body>
  <script type="module">
    import parser from "https://unpkg.com/yargs-parser@19.0.0/browser.js";

    const argv = parser('--foo=99 --bar=9987930', {
      string: ['bar']
    })
    console.log(argv)
  </script>
</body>

API

parser(args, opts={})

Parses command line arguments returning a simple mapping of keys and values.

expects:

  • args: a string or array of strings representing the options to parse.
  • opts: provide a set of hints indicating how args should be parsed:
    • opts.alias: an object representing the set of aliases for a key: {alias: {foo: ['f']}}.
    • opts.array: indicate that keys should be parsed as an array: {array: ['foo', 'bar']}.
      Indicate that keys should be parsed as an array and coerced to booleans / numbers:
      {array: [{ key: 'foo', boolean: true }, {key: 'bar', number: true}]}.
    • opts.boolean: arguments should be parsed as booleans: {boolean: ['x', 'y']}.
    • opts.coerce: provide a custom synchronous function that returns a coerced value from the argument provided (or throws an error). For arrays the function is called only once for the entire array:
      {coerce: {foo: function (arg) {return modifiedArg}}}.
    • opts.config: indicate a key that represents a path to a configuration file (this file will be loaded and parsed).
    • opts.configObjects: configuration objects to parse, their properties will be set as arguments:
      {configObjects: [{'x': 5, 'y': 33}, {'z': 44}]}.
    • opts.configuration: provide configuration options to the yargs-parser (see: configuration).
    • opts.count: indicate a key that should be used as a counter, e.g., -vvv = {v: 3}.
    • opts.default: provide default values for keys: {default: {x: 33, y: 'hello world!'}}.
    • opts.envPrefix: environment variables (process.env) with the prefix provided should be parsed.
    • opts.narg: specify that a key requires n arguments: {narg: {x: 2}}.
    • opts.normalize: path.normalize() will be applied to values set to this key.
    • opts.number: keys should be treated as numbers.
    • opts.string: keys should be treated as strings (even if they resemble a number -x 33).

returns:

  • obj: an object representing the parsed value of args
    • key/value: key value pairs for each argument and their aliases.
    • _: an array representing the positional arguments.
    • [optional] --: an array with arguments after the end-of-options flag --.

require('yargs-parser').detailed(args, opts={})

Parses a command line string, returning detailed information required by the yargs engine.

expects:

  • args: a string or array of strings representing options to parse.
  • opts: provide a set of hints indicating how args, inputs are identical to require('yargs-parser')(args, opts={}).

returns:

  • argv: an object representing the parsed value of args
    • key/value: key value pairs for each argument and their aliases.
    • _: an array representing the positional arguments.
    • [optional] --: an array with arguments after the end-of-options flag --.
  • error: populated with an error object if an exception occurred during parsing.
  • aliases: the inferred list of aliases built by combining lists in opts.alias.
  • newAliases: any new aliases added via camel-case expansion:
    • boolean: { fooBar: true }
  • defaulted: any new argument created by opts.default, no aliases included.
    • boolean: { foo: true }
  • configuration: given by default settings and opts.configuration.

Configuration

The yargs-parser applies several automated transformations on the keys provided in args. These features can be turned on and off using the configuration field of opts.

var parsed = parser(['--no-dice'], {
  configuration: {
    'boolean-negation': false
  }
})

short option groups

  • default: true.
  • key: short-option-groups.

Should a group of short-options be treated as boolean flags?

$ node example.js -abc
{ _: [], a: true, b: true, c: true }

if disabled:

$ node example.js -abc
{ _: [], abc: true }

camel-case expansion

  • default: true.
  • key: camel-case-expansion.

Should hyphenated arguments be expanded into camel-case aliases?

$ node example.js --foo-bar
{ _: [], 'foo-bar': true, fooBar: true }

if disabled:

$ node example.js --foo-bar
{ _: [], 'foo-bar': true }

dot-notation

  • default: true
  • key: dot-notation

Should keys that contain . be treated as objects?

$ node example.js --foo.bar
{ _: [], foo: { bar: true } }

if disabled:

$ node example.js --foo.bar
{ _: [], "foo.bar": true }

parse numbers

  • default: true
  • key: parse-numbers

Should keys that look like numbers be treated as such?

$ node example.js --foo=99.3
{ _: [], foo: 99.3 }

if disabled:

$ node example.js --foo=99.3
{ _: [], foo: "99.3" }

parse positional numbers

  • default: true
  • key: parse-positional-numbers

Should positional keys that look like numbers be treated as such.

$ node example.js 99.3
{ _: [99.3] }

if disabled:

$ node example.js 99.3
{ _: ['99.3'] }

boolean negation

  • default: true
  • key: boolean-negation

Should variables prefixed with --no be treated as negations?

$ node example.js --no-foo
{ _: [], foo: false }

if disabled:

$ node example.js --no-foo
{ _: [], "no-foo": true }

combine arrays

  • default: false
  • key: combine-arrays

Should arrays be combined when provided by both command line arguments and a configuration file.

duplicate arguments array

  • default: true
  • key: duplicate-arguments-array

Should arguments be coerced into an array when duplicated:

$ node example.js -x 1 -x 2
{ _: [], x: [1, 2] }

if disabled:

$ node example.js -x 1 -x 2
{ _: [], x: 2 }

flatten duplicate arrays

  • default: true
  • key: flatten-duplicate-arrays

Should array arguments be coerced into a single array when duplicated:

$ node example.js -x 1 2 -x 3 4
{ _: [], x: [1, 2, 3, 4] }

if disabled:

$ node example.js -x 1 2 -x 3 4
{ _: [], x: [[1, 2], [3, 4]] }

greedy arrays

  • default: true
  • key: greedy-arrays

Should arrays consume more than one positional argument following their flag.

$ node example --arr 1 2
{ _: [], arr: [1, 2] }

if disabled:

$ node example --arr 1 2
{ _: [2], arr: [1] }

Note: in v18.0.0 we are considering defaulting greedy arrays to false.

nargs eats options

  • default: false
  • key: nargs-eats-options

Should nargs consume dash options as well as positional arguments.

negation prefix

  • default: no-
  • key: negation-prefix

The prefix to use for negated boolean variables.

$ node example.js --no-foo
{ _: [], foo: false }

if set to quux:

$ node example.js --quuxfoo
{ _: [], foo: false }

populate --

  • default: false.
  • key: populate--

Should unparsed flags be stored in -- or _.

If disabled:

$ node example.js a -b -- x y
{ _: [ 'a', 'x', 'y' ], b: true }

If enabled:

$ node example.js a -b -- x y
{ _: [ 'a' ], '--': [ 'x', 'y' ], b: true }

set placeholder key

  • default: false.
  • key: set-placeholder-key.

Should a placeholder be added for keys not set via the corresponding CLI argument?

If disabled:

$ node example.js -a 1 -c 2
{ _: [], a: 1, c: 2 }

If enabled:

$ node example.js -a 1 -c 2
{ _: [], a: 1, b: undefined, c: 2 }

halt at non-option

  • default: false.
  • key: halt-at-non-option.

Should parsing stop at the first positional argument? This is similar to how e.g. ssh parses its command line.

If disabled:

$ node example.js -a run b -x y
{ _: [ 'b' ], a: 'run', x: 'y' }

If enabled:

$ node example.js -a run b -x y
{ _: [ 'b', '-x', 'y' ], a: 'run' }

strip aliased

  • default: false
  • key: strip-aliased

Should aliases be removed before returning results?

If disabled:

$ node example.js --test-field 1
{ _: [], 'test-field': 1, testField: 1, 'test-alias': 1, testAlias: 1 }

If enabled:

$ node example.js --test-field 1
{ _: [], 'test-field': 1, testField: 1 }

strip dashed

  • default: false
  • key: strip-dashed

Should dashed keys be removed before returning results? This option has no effect if camel-case-expansion is disabled.

If disabled:

$ node example.js --test-field 1
{ _: [], 'test-field': 1, testField: 1 }

If enabled:

$ node example.js --test-field 1
{ _: [], testField: 1 }

unknown options as args

  • default: false
  • key: unknown-options-as-args

Should unknown options be treated like regular arguments? An unknown option is one that is not configured in opts.

If disabled

$ node example.js --unknown-option --known-option 2 --string-option --unknown-option2
{ _: [], unknownOption: true, knownOption: 2, stringOption: '', unknownOption2: true }

If enabled

$ node example.js --unknown-option --known-option 2 --string-option --unknown-option2
{ _: ['--unknown-option'], knownOption: 2, stringOption: '--unknown-option2' }

Supported Node.js Versions

Libraries in this ecosystem make a best effort to track Node.js' release schedule. Here's a post on why we think this is important.

Special Thanks

The yargs project evolves from optimist and minimist. It owes its existence to a lot of James Halliday's hard work. Thanks substack beep boop \o/

License

ISC

changelog

Changelog

All notable changes to this project will be documented in this file. See standard-version for commit guidelines.

21.1.1 (2022-08-04)

Bug Fixes

  • typescript: ignore .cts files during publish (#454) (d69f9c3), closes #452

21.1.0 (2022-08-03)

Features

  • allow the browser build to be imported (#443) (a89259f)

Bug Fixes

  • halt-at-non-option: prevent known args from being parsed when "unknown-options-as-args" is enabled (#438) (c474bc1)
  • node version check now uses process.versions.node (#450) (d07bcdb)
  • parse options ending with 3+ hyphens (#434) (4f1060b)

21.0.1 (2022-02-27)

Bug Fixes

21.0.0 (2021-11-15)

⚠ BREAKING CHANGES

  • drops support for 10 (#421)

Bug Fixes

Code Refactoring

20.2.9 (2021-06-20)

Bug Fixes

  • build: fixed automated release pipeline (1fe9135)

20.2.8 (2021-06-20)

Bug Fixes

  • locale: Turkish camelize and decamelize issues with toLocaleLowerCase/toLocaleUpperCase (2617303)
  • perf: address slow parse when using unknown-options-as-args (#394) (441f059)
  • string-utils: detect [0,1] ranged values as numbers (#388) (efcc32c)

20.2.7 (2021-03-10)

Bug Fixes

  • deno: force release for Deno (6687c97)

20.2.6 (2021-02-22)

Bug Fixes

  • populate--: -- should always be array (#354) (585ae8f)

20.2.5 (2021-02-13)

Bug Fixes

20.2.4 (2020-11-09)

Bug Fixes

20.2.3 (2020-10-16)

Bug Fixes

  • exports: node 13.0 and 13.1 require the dotted object form with a string fallback (#336) (3ae7242)

20.2.2 (2020-10-14)

Bug Fixes

  • exports: node 13.0-13.6 require a string fallback (#333) (291aeda)

20.2.1 (2020-10-01)

Bug Fixes

20.2.0 (2020-09-21)

Features

  • string-utils: export looksLikeNumber helper (#324) (c8580a2)

Bug Fixes

  • unknown-options-as-args: convert positionals that look like numbers (#326) (f85ebb4)

20.1.0 (2020-09-20)

Features

  • adds parse-positional-numbers configuration (#321) (9cec00a)

Bug Fixes

  • build: update release-please; make labels kick off builds (#323) (09f448b)

20.0.0 (2020-09-09)

⚠ BREAKING CHANGES

  • do not ship type definitions (#318)

Bug Fixes

Code Refactoring

19.0.4 (2020-08-27)

Bug Fixes

19.0.3 (2020-08-27)

Bug Fixes

19.0.2 (2020-08-27)

Bug Fixes

19.0.1 (2020-08-09)

Bug Fixes

  • build: push tag created for deno (2186a14)

19.0.0 (2020-08-09)

⚠ BREAKING CHANGES

  • adds support for ESM and Deno (#295)
  • ts: projects using @types/yargs-parser may see variations in type definitions.
  • drops Node 6. begin following Node.js LTS schedule (#278)

Features

  • adds support for ESM and Deno (#295) (195bc4a)
  • expose camelCase and decamelize helpers (#296) (39154ce)
  • deps: update to latest camelcase/decamelize (#281) (8931ab0)

Bug Fixes

  • boolean numeric short option (#294) (f600082)
  • raise permission error for Deno if config load fails (#298) (1174e2b)
  • deps: update dependency decamelize to v3 (#274) (4d98698)
  • types: switch back to using Partial types (#293) (bdc80ba)

Build System

  • drops Node 6. begin following Node.js LTS schedule (#278) (9014ed7)

Code Refactoring

18.1.3 (2020-04-16)

Bug Fixes

  • setArg: options using camel-case and dot-notation populated twice (#268) (f7e15b9)

18.1.2 (2020-03-26)

Bug Fixes

  • array, nargs: support -o=--value and --option=--value format (#262) (41d3f81)

18.1.1 (2020-03-16)

Bug Fixes

  • __proto__ will now be replaced with ___proto___ in parse (#258), patching a potential prototype pollution vulnerability. This was reported by the Snyk Security Research Team.(63810ca)

18.1.0 (2020-03-07)

Features

  • introduce single-digit boolean aliases (#255) (9c60265)

18.0.0 (2020-03-02)

⚠ BREAKING CHANGES

  • the narg count is now enforced when parsing arrays.

Features

  • NaN can now be provided as a value for nargs, indicating "at least" one value is expected for array (#251) (9db4be8)

17.1.0 (2020-03-01)

Features

  • introduce greedy-arrays config, for specifying whether arrays consume multiple positionals (#249) (60e880a)

17.0.1 (2020-02-29)

Bug Fixes

17.0.0 (2020-02-10)

⚠ BREAKING CHANGES

  • this reverts parsing behavior of booleans to that of yargs@14
  • objects used during parsing are now created with a null prototype. There may be some scenarios where this change in behavior leaks externally.

Features

  • boolean arguments will not be collected into an implicit array (#236) (34c4e19)
  • introduce nargs-eats-options config option (#246) (d50822a)

Bug Fixes

  • address bugs with "uknown-options-as-args" (bc023e3)
  • array should take precedence over nargs, but enforce nargs (#243) (4cbc188)
  • support keys that collide with object prototypes (#234) (1587b6d)
  • unknown options terminated with digits now handled by unknown-options-as-args (#238) (d36cdfa)

16.1.0 (2019-11-01)

⚠ BREAKING CHANGES

  • populate error if incompatible narg/count or array/count options are used (#191)

Features

  • options that have had their default value used are now tracked (#211) (a525234)
  • populate error if incompatible narg/count or array/count options are used (#191) (84a401f)

Reverts

  • revert 16.0.0 CHANGELOG entry (920320a)