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The mighty option parser used by yargs.

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


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

or parse a string!

var argv = require('./')('--foo=99 --bar=33')
{ _: [], 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


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

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


  • 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']}.
    • opts.boolean: arguments should be parsed as booleans: {boolean: ['x', 'y']}.
    • opts.config: indicate a key that represents a path to a configuration file (this file will be loaded and parsed).
    • opts.coerce: provide a custom synchronous function that returns a coerced value from the argument provided (or throws an error), e.g. {coerce: {foo: function (arg) {return modifiedArg}}}.
    • 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.string: keys should be treated as strings (even if they resemble a number -x 33).
    • opts.configuration: provide configuration options to the yargs-parser (see: configuration).
    • opts.number: keys should be treated as numbers.
    • opts['--']: arguments after the end-of-options flag -- will be set to the argv.['--'] array instead of being set to the argv._ array.


  • 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.


  • 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={}).


  • 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.
  • 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.
  • configuration: the configuration loaded from the yargs stanza in package.json.


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 }


  • default: true
  • key: dot-notation

Should keys that contain . be treated as objects?

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

if disabled:

node example.js
{ _: [], ""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]] }

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 }

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/