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:

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](https://medium.com/the-node-js-collection/maintainers-should-consider-following-node-js-release-schedule-ab08ed4de71a).

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

📄 README.md

yargs-parser

Example

Deno Example

ESM Example

API

parser(args, opts={})

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

Configuration

short option groups

camel-case expansion

dot-notation

parse numbers

parse positional numbers

boolean negation

combine arrays

duplicate arguments array

flatten duplicate arrays

greedy arrays

nargs eats options

negation prefix

populate --

set placeholder key

halt at non-option

strip aliased

strip dashed

unknown options as args

Supported Node.js Versions

Special Thanks

License