13.2.4

Yargs

Yargs be a node.js library fer hearties tryin' ter parse optstrings

Description

Yargs helps you build interactive command line tools, by parsing arguments and generating an elegant user interface.

It gives you:

• commands and (grouped) options (my-program.js serve --port=5000).
• a dynamically generated help menu based on your arguments:

mocha [spec..]

Run tests with Mocha

Commands
  mocha inspect [spec..]  Run tests with Mocha                         [default]
  mocha init <path>       create a client-side Mocha setup at <path>

Rules & Behavior
  --allow-uncaught           Allow uncaught errors to propagate        [boolean]
  --async-only, -A           Require all tests to use a callback (async) or
                             return a Promise                          [boolean]

• generate completion scripts for Bash and Zsh for your command
• and tons more.

Installation

Stable version:

npm i yargs

Bleeding edge version with the most recent features:

npm i yargs@next

Usage

Simple Example

#!/usr/bin/env node
import yargs from 'yargs';
import { hideBin } from 'yargs/helpers';
const argv = yargs(hideBin(process.argv)).parse()

if (argv.ships > 3 && argv.distance < 53.5) {
  console.log('Plunder more riffiwobbles!')
} else {
  console.log('Retreat from the xupptumblers!')
}

$ ./plunder.js --ships=4 --distance=22
Plunder more riffiwobbles!

$ ./plunder.js --ships 12 --distance 98.7
Retreat from the xupptumblers!

Note: hideBin is a shorthand for process.argv.slice(2). It has the benefit that it takes into account variations in some environments, e.g., Electron.

Complex Example

#!/usr/bin/env node
import yargs from 'yargs';
import { hideBin } from 'yargs/helpers';

yargs(hideBin(process.argv))
  .command('serve [port]', 'start the server', (yargs) => {
    return yargs
      .positional('port', {
        describe: 'port to bind on',
        default: 5000
      })
  }, (argv) => {
    if (argv.verbose) console.info(`start server on :${argv.port}`)
    serve(argv.port)
  })
  .option('verbose', {
    alias: 'v',
    type: 'boolean',
    description: 'Run with verbose logging'
  })
  .parse()

Run the example above with --help to see the help for the application.

Supported Platforms

TypeScript

yargs has type definitions at @types/yargs.

npm i @types/yargs --save-dev

See usage examples in docs.

Deno

As of v16, yargs supports Deno:

import yargs from 'https://deno.land/x/yargs@v17.7.2-deno/deno.ts'
import { Arguments } from 'https://deno.land/x/yargs@v17.7.2-deno/deno-types.ts'

yargs(Deno.args)
  .command('download <files...>', 'download a list of files', (yargs: any) => {
    return yargs.positional('files', {
      describe: 'a list of files to do something with'
    })
  }, (argv: Arguments) => {
    console.info(argv)
  })
  .strictCommands()
  .demandCommand(1)
  .parse()

Note: If you use version tags in url then you also have to add -deno flag on the end, like @17.7.2-deno

Usage in Browser

See examples of using yargs in the browser in docs.

Documentation

Table of Contents

• Yargs' API
• Examples
• Parsing Tricks
  • Stop the Parser
  • Negating Boolean Arguments
  • Numbers
  • Arrays
  • Objects
  • Quotes
• Advanced Topics
  • Composing Your App Using Commands
  • Building Configurable CLI Apps
  • Customizing Yargs' Parser
• Contributing

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.