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meow
Advanced tools
Package description
The 'meow' npm package is a CLI helper that simplifies the process of writing command-line applications in Node.js. It parses arguments, generates help text, and handles errors.
Argument Parsing
Meow parses command-line arguments and options, making them easily accessible within your application.
const meow = require('meow');
const cli = meow(`
Usage
$ foo <input>
`);
console.log(cli.input); //=> ['inputValue']
console.log(cli.flags); //=> {flagName: flagValue}
Help Text Generation
Meow automatically generates and displays help text for your CLI application based on a template you provide.
const meow = require('meow');
const cli = meow(`
Usage
$ foo <input>
Options
--rainbow, -r Include a rainbow
`);
// If the user runs the command with `--help`, meow will automatically display the help text.
Flags Customization
Meow allows you to define and customize flags for your CLI application, including setting aliases and default values.
const meow = require('meow');
const cli = meow(`
Usage
$ foo <input>
`, {
flags: {
rainbow: {
type: 'boolean',
alias: 'r'
}
}
});
console.log(cli.flags.rainbow); //=> true or false
Yargs is a powerful npm package that helps you build interactive command-line tools, by parsing arguments and generating an elegant user interface. It's more feature-rich than meow, providing a wide range of options for argument parsing, command handling, and validation.
Commander is another npm package for writing command-line applications. It's similar to meow but offers a more object-oriented approach to defining commands and options. Commander is well-suited for complex CLI applications with sub-commands.
Minimist is a minimalistic argument parsing library. Unlike meow, it focuses solely on parsing command-line arguments without any additional features like help text generation or input validation.
Readme
CLI app helper
--no-
prefix--version
--help
$ npm install meow
$ ./foo-app.js unicorns --rainbow
#!/usr/bin/env node
'use strict';
const meow = require('meow');
const foo = require('.');
const cli = meow(`
Usage
$ foo <input>
Options
--rainbow, -r Include a rainbow
Examples
$ foo unicorns --rainbow
🌈 unicorns 🌈
`, {
flags: {
rainbow: {
type: 'boolean',
alias: 'r'
}
}
});
/*
{
input: ['unicorns'],
flags: {rainbow: true},
...
}
*/
foo(cli.input[0], cli.flags);
Returns an object
with:
input
(Array) - Non-flag argumentsflags
(Object) - Flags converted to camelCase excluding aliasesunnormalizedFlags
(Object) - Flags converted to camelCase including aliasespkg
(Object) - The package.json
objecthelp
(string) - The help text used with --help
showHelp([exitCode=2])
(Function) - Show the help text and exit with exitCode
showVersion()
(Function) - Show the version text and exitType: string
Shortcut for the help
option.
Type: object
Type: object
Define argument flags.
The key is the flag name and the value is an object with any of:
type
: Type of value. (Possible values: string
boolean
number
)alias
: Usually used to define a short flag alias.default
: Default value when the flag is not specified.Example:
flags: {
unicorn: {
type: 'string',
alias: 'u',
default: 'rainbow'
}
}
Type: string | boolean
Default: The package.json "description"
property
Description to show above the help text.
Set it to false
to disable it altogether.
Type: string | boolean
The help text you want shown.
The input is reindented and starting/ending newlines are trimmed which means you can use a template literal without having to care about using the correct amount of indent.
The description will be shown above your help text automatically.
Type: string | boolean
Default: The package.json "version"
property
Set a custom version output.
Type: boolean
Default: true
Automatically show the help text when the --help
flag is present. Useful to set this value to false
when a CLI manages child CLIs with their own help text.
This option is only considered when there is only one argument in process.argv
.
Type: boolean
Default: true
Automatically show the version text when the --version
flag is present. Useful to set this value to false
when a CLI manages child CLIs with their own version text.
This option is only considered when there is only one argument in process.argv
.
Type: object
Default: Closest package.json upwards
package.json as an object
.
You most likely don't need this option.
Type: string[]
Default: process.argv.slice(2)
Custom arguments object.
Type: boolean
Default: false
Infer the argument type.
By default, the argument 5
in $ foo 5
becomes a string. Enabling this would infer it as a number.
Type: boolean | null | undefined
Default: false
Value of boolean
flags not defined in argv
.
If set to undefined
the flags not defined in argv
will be excluded from the result.
The default
value set in boolean
flags take precedence over booleanDefault
.
Example:
const meow = require('meow');
const cli = meow(`
Usage
$ foo
Options
--rainbow, -r Include a rainbow
--unicorn, -u Include a unicorn
--no-sparkles Exclude sparkles
Examples
$ foo
🌈 unicorns✨🌈
`, {
booleanDefault: undefined,
flags: {
rainbow: {
type: 'boolean',
default: true,
alias: 'r'
},
unicorn: {
type: 'boolean',
default: false,
alias: 'u'
},
cake: {
type: 'boolean',
alias: 'c'
},
sparkles: {
type: 'boolean',
default: true
}
}
});
/*
{
flags: {
rainbow: true,
unicorn: false,
sparkles: true
},
unnormalizedFlags: {
rainbow: true,
r: true,
unicorn: false,
u: false,
sparkles: true
},
…
}
*/
Type: boolean
Default: true
Whether to use hard-rejection
or not. Disabling this can be useful if you need to handle process.on('unhandledRejection')
yourself.
Meow will make unhandled rejected promises fail hard instead of the default silent fail. Meaning you don't have to manually .catch()
promises used in your CLI.
See chalk
if you want to colorize the terminal output.
See get-stdin
if you want to accept input from stdin.
See conf
if you need to persist some data.
See update-notifier
if you want update notifications.
FAQs
CLI app helper
We found that meow demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
Did you know?
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