How do I pass command line arguments to a Node.js program?

Question

I have a web server written in Node.js and I would like to launch with a specific folder. I\'m not sure how to access arguments in JavaScript. I\'m running node like this:

Answer 1

Stdio Library

The easiest way to parse command-line arguments in NodeJS is using the stdio module. Inspired by UNIX getopt utility, it is as trivial as follows:

var stdio = require('stdio');
var ops = stdio.getopt({
    'check': {key: 'c', args: 2, description: 'What this option means'},
    'map': {key: 'm', description: 'Another description'},
    'kaka': {args: 1, required: true},
    'ooo': {key: 'o'}
});

If you run the previous code with this command:

node  -c 23 45 --map -k 23 file1 file2

Then ops object will be as follows:

{ check: [ '23', '45' ],
  args: [ 'file1', 'file2' ],
  map: true,
  kaka: '23' }

So you can use it as you want. For instance:

if (ops.kaka && ops.check) {
    console.log(ops.kaka + ops.check[0]);
}

Grouped options are also supported, so you can write -om instead of -o -m.

Furthermore, stdio can generate a help/usage output automatically. If you call ops.printHelp() you'll get the following:

USAGE: node something.js [--check  ] [--kaka] [--ooo] [--map]
  -c, --check     What this option means (mandatory)
  -k, --kaka                  (mandatory)
  --map                       Another description
  -o, --ooo

The previous message is shown also if a mandatory option is not given (preceded by the error message) or if it is mispecified (for instance, if you specify a single arg for an option and it needs 2).

You can install stdio module using NPM:

npm install stdio