The mighty option parser used by yargs.

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

Example

npm i yargs-parser --save

var 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!

var 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:

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

API

require('yargs-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<tt>: 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<tt>: 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<tt>: provide configuration options to the yargs-parser (see: [configuration](#configuration)). *opts.count<tt>: indicate a key that should be used as a counter, e.g.,-vvv={v: 3}. *opts.default<tt>: provide default values for keys:{default: {x: 33, y: 'hello world!'}}. *opts.envPrefix<tt>: environment variables (process.env<tt>) with the prefix provided should be parsed. *opts.narg<tt>: specify that a key requiresnarguments:{narg: {x: 2}}. *opts.normalize<tt>:path.normalize()will be applied to values set to this key. *opts.number<tt>: keys should be treated as numbers. *opts.string<tt>: 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" }

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' }

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