Optimist – A Node.js Module You Should Know About

Hey everyone! This is the second post in my new node.js modules you should know about article series.

The first post was about dnode - the freestyle rpc library for node.

This time I'll introduce you to node-optimist - the lightweight options parser library. This library is also written by James Halliday (SubStack), my co-founder of Browserling and Testling.

Wonder how lightweight an options parser can be? Check this out:

var argv = require('optimist').argv;

And you're done! All options have been parsed for you and have been put in argv.

Here are various use cases. First off, it supports long arguments:

#!/usr/bin/env node
var argv = require('optimist').argv;

if (argv.rif - 5 * argv.xup > 7.138) {
    console.log('Buy more riffiwobbles');
}
else {
    console.log('Sell the xupptumblers');
}

Now you can run this script with --rif and --xup arguments like this:

$ ./xup.js --rif=55 --xup=9.52
Buy more riffiwobbles

$ ./xup.js --rif 12 --xup 8.1
Sell the xupptumblers

I know you want to buy more riffiwobbles and sell your xupptumblers.

Next, it supports short args:

#!/usr/bin/env node
var argv = require('optimist').argv;
console.log('(%d,%d)', argv.x, argv.y);

You can use -x and -y as arguments:

$ ./short.js -x 10 -y 21
(10,21)

Then node-optimist supports boolean arguments, both short, long and grouped:

#!/usr/bin/env node
var argv = require('optimist').argv;

if (argv.s) {
    console.log(argv.fr ? 'Le chat dit: ' : 'The cat says: ');
}
console.log(
    (argv.fr ? 'miaou' : 'meow') + (argv.p ? '.' : '')
);

And now you can invoke the script with various options:

$ ./bool.js -s
The cat says: meow

$ ./bool.js -sp
The cat says: meow.

$ ./bool.js -sp --fr
Le chat dit: miaou.

Next, you can easily get to non-hypenated options via argv._:

#!/usr/bin/env node
var argv = require('optimist').argv;

console.log('(%d,%d)', argv.x, argv.y);
console.log(argv._);

Here are use cases for non-hypenated options:

$ ./nonopt.js -x 6.82 -y 3.35 moo
(6.82,3.35)
[ 'moo' ]

$ ./nonopt.js foo -x 0.54 bar -y 1.12 baz
(0.54,1.12)
[ 'foo', 'bar', 'baz' ]

Optimist also comes with .usage() and .demand() functions:

#!/usr/bin/env node
var argv = require('optimist')
    .usage('Usage: $0 -x [num] -y [num]')
    .demand(['x','y'])
    .argv;

console.log(argv.x / argv.y);

Here arguments x and y are required and if they are not passed, the usage will be printed automatically:

$ ./divide.js -x 55 -y 11
5

$ node ./divide.js -x 4.91 -z 2.51
Usage: node ./divide.js -x [num] -y [num]

Options:
  -x  [required]
  -y  [required]

Missing required arguments: y

Optimist also supports default arguments via .default():

#!/usr/bin/env node
var argv = require('optimist')
    .default('x', 10)
    .default('y', 10)
    .argv
;
console.log(argv.x + argv.y);

Here x and y default to 10:

$ ./default_singles.js -x 5
15

Enjoy this stranger:

Alternatively you can use isaacs's nopt that can enforce data types on arguments and can be used to easily handle a lot of arguments. Or you can use nomnom that noms your args and gives them back to you in a hash.