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# yargs-parser  [](https://www.npmjs.com/package/yargs-parser) [](https://conventionalcommits.org)  The mighty option parser used by [yargs](https://github.com/yargs/yargs). visit the [yargs website](http://yargs.js.org/) for more examples, and thorough usage instructions. <img width="250" src="https://raw.githubusercontent.com/yargs/yargs-parser/main/yargs-logo.png"> ## Example ```sh npm i yargs-parser --save ``` ```js const argv = require('yargs-parser')(process.argv.slice(2)) console.log(argv) ``` ```console $ node example.js --foo=33 --bar hello { _: [], foo: 33, bar: 'hello' } ``` _or parse a string!_ ```js const argv = require('yargs-parser')('--foo=99 --bar=33') console.log(argv) ``` ```console { _: [], foo: 99, bar: 33 } ``` Convert an array of mixed types before passing to `yargs-parser`: ```js 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](https://github.com/denoland/deno): ```typescript 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:** ```js import parser from 'yargs-parser' const argv = parser('--foo=99 --bar=9987930', { string: ['bar'] }) console.log(argv) ``` **Browsers:** ```html <!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']}`.<br> Indicate that keys should be parsed as an array and coerced to booleans / numbers:<br> `{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:<br> `{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:<br> `{configObjects: [{'x': 5, 'y': 33}, {'z': 44}]}`. * `opts.configuration`: provide configuration options to the yargs-parser (see: [configuration](#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`. <a name="configuration"></a> ### 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`. ```js 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? ```console $ node example.js -abc { _: [], a: true, b: true, c: true } ``` _if disabled:_ ```console $ node example.js -abc { _: [], abc: true } ``` ### camel-case expansion * default: `true`. * key: `camel-case-expansion`. Should hyphenated arguments be expanded into camel-case aliases? ```console $ node example.js --foo-bar { _: [], 'foo-bar': true, fooBar: true } ``` _if disabled:_ ```console $ node example.js --foo-bar { _: [], 'foo-bar': true } ``` ### dot-notation * default: `true` * key: `dot-notation` Should keys that contain `.` be treated as objects? ```console $ node example.js --foo.bar { _: [], foo: { bar: true } } ``` _if disabled:_ ```console $ 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? ```console $ node example.js --foo=99.3 { _: [], foo: 99.3 } ``` _if disabled:_ ```console $ 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. ```console $ node example.js 99.3 { _: [99.3] } ``` _if disabled:_ ```console $ node example.js 99.3 { _: ['99.3'] } ``` ### boolean negation * default: `true` * key: `boolean-negation` Should variables prefixed with `--no` be treated as negations? ```console $ node example.js --no-foo { _: [], foo: false } ``` _if disabled:_ ```console $ 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: ```console $ node example.js -x 1 -x 2 { _: [], x: [1, 2] } ``` _if disabled:_ ```console $ 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: ```console $ node example.js -x 1 2 -x 3 4 { _: [], x: [1, 2, 3, 4] } ``` _if disabled:_ ```console $ 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. ```console $ node example --arr 1 2 { _: [], arr: [1, 2] } ``` _if disabled:_ ```console $ 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. ```console $ node example.js --no-foo { _: [], foo: false } ``` _if set to `quux`:_ ```console $ node example.js --quuxfoo { _: [], foo: false } ``` ### populate -- * default: `false`. * key: `populate--` Should unparsed flags be stored in `--` or `_`. _If disabled:_ ```console $ node example.js a -b -- x y { _: [ 'a', 'x', 'y' ], b: true } ``` _If enabled:_ ```console $ 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:_ ```console $ node example.js -a 1 -c 2 { _: [], a: 1, c: 2 } ``` _If enabled:_ ```console $ 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:_ ```console $ node example.js -a run b -x y { _: [ 'b' ], a: 'run', x: 'y' } ``` _If enabled:_ ```console $ 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:_ ```console $ node example.js --test-field 1 { _: [], 'test-field': 1, testField: 1, 'test-alias': 1, testAlias: 1 } ``` _If enabled:_ ```console $ 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:_ ```console $ node example.js --test-field 1 { _: [], 'test-field': 1, testField: 1 } ``` _If enabled:_ ```console $ 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_ ```console $ node example.js --unknown-option --known-option 2 --string-option --unknown-option2 { _: [], unknownOption: true, knownOption: 2, stringOption: '', unknownOption2: true } ``` _If enabled_ ```console $ 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](https://nodejs.org/en/about/releases/). 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](https://github.com/substack) **beep** **boop** \o/ ## License ISC