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Ahoy! Parse ye Node.js command args with yargs!

April 20, 2015

Recently I was working on a code sample in Node.js and thought to meself, "T'wouldn't it be grand to support me some command-line args for this here..." or... something to that effect. So, with a quick Google off the port bow, I came across yargs.

Yargs be a node.js library fer hearties tryin' ter parse optstrings. With yargs, ye be havin' a map that leads straight to yer treasure! Treasure of course, being a simple option hash.

Yargs makes it easy to support command-line arguments for Node.js application. Check out the LeanKit search sample application I created that uses yargs.

Here be a quick example for ye

Imagine we plan to create our own version of curl named "jurl", implemented in Node.js specifically for REST and JSON. Our first pass at the arguments we want to support might look like this:

var options = require( "yargs" )
 .usage( "Usage: $0 <url> [-u \"username\"] [-p \"password\"] [--post] [--data \"{key:value}\"]" )
 .command( "url", "URL to request", { alias: "url" } )
 .required( 1, "URL is required" )
 .option( "u", { alias: "user", demand: false, describe: "Username", type: "string" } )
 .option( "p", { alias: "password", demand: false, describe: "Password", type: "string" } )
 .option( "d", { alias: "data", describe: "Data to send as JSON", type: "string" } )
 .option( "get", { describe: "Use HTTP GET", type: "boolean" } )
 .option( "post", { describe: "Use HTTP POST", type: "boolean" } )
 .option( "put", { describe: "Use HTTP PUT", type: "boolean" } )
 .option( "del", { describe: "Use HTTP DELETE", type: "boolean" } )
 .help( "?" )
 .alias( "?", "help" )
 .example( "$0", "Get a list of posts" )
 .example( "$0 --post --data \"{ 'title': 'Avast ye!', 'body': 'Thar be a post hyar!'}\"", "Create a new post" )
 .epilog( "Copyright 2015 ReverentGeek" )

// Get the URL from the first parameter
var url = options._[ 0 ];

// Make "get" the default if no verb is specified
if ( !options.get && ! && !options.put && !options.del ) {
 options.get = true;

console.log( "url:", url );
console.log( "options:", options );

Take a look at the command-line help yargs creates for ye.

$ node jurl --help
Usage: jurl <url> [-u "username"] [-p "password"] [--post] [--data

  url    URL to request

  -u, --user      Username                                              [string]
  -p, --password  Password                                              [string]
  -d, --data      Data to send as JSON                                  [string]
  --get           Use HTTP GET                                         [boolean]
  --post          Use HTTP POST                                        [boolean]
  --put           Use HTTP PUT                                         [boolean]
  --del           Use HTTP DELETE                                      [boolean]
  -?, --help      Show help

  jurl          Get a list of posts
  jurl          Create a new post
  --post --data "{ 'title': 'Avast
  ye!', 'body': 'Thar be a post hyar!'}"

Copyright 2015 ReverentGeek

Running the given sample prints the following to the console.

$ node jurl
options: { _: [ '' ],
  get: true,
  post: false,
  put: false,
  del: false,
  '$0': 'jurl',
  u: undefined,
  p: undefined,
  d: undefined,
  '?': undefined }

Hoist the mizzen, sail forth and blast ye command ARRRRGS to smithereens!