• We have a web server written in Node.js that we would like to launch with a specific folder. Does not sure how to access arguments in JavaScript.

Here running node like this:

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$ node server.js folder
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Where server.js is the code.

$ node -h
Usage: node [options] script.js [arguments]

How to access those arguments in JavaScript?

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Javjavascript           node.js        arguments              command-line-argumentsascript

The arguments are stored in process.argv

process.argv is an array containing the command line arguments. The first element will be ‘node’, the second element will be the name of the JavaScript file. The next elements will be any additional command line arguments.

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// print process.argv
process.argv.forEach(function (val, index, array) {
  console.log(index + ': ' + val);
});

This will generate:

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$ node process-2.js one two=three four
0: node
1: /Users/mjr/work/node/process-2.js
2: one
3: two=three
4: four

  • To normalize the arguments like a regular javascript function would receive, we do this in my node.js shell scripts:
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var args = process.argv.slice(2);

Note : The first arg is usually the path to nodejs, and the second arg is the location of the script you’re executing.

  • To use the minimist library. We can use node-optimist but it has since been deprecated.

Here is an example of how to use it taken straight from the minimist documentation:

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var argv = require('minimist')(process.argv.slice(2));
console.dir(argv);
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$ node example/parse.js -a beep -b boop
{ _: [], a: 'beep', b: 'boop' }
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$ node example/parse.js -x 3 -y 4 -n5 -abc --beep=boop foo bar baz
{ _: [ 'foo', 'bar', 'baz' ],
  x: 3,
  y: 4,
  n: 5,
  a: true,
  b: true,
  c: true,
  beep: 'boop' }

  • Vanilla javascript argument parsing:
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const args = process.argv;
console.log(args);

This returns:

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$ node process-2.js one two=three four
['node', '/Users/dc/node/server.js', 'one', 'two=three', 'four']

  • This is very similar to how bash scripts access argument values.
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$ node yourscript.js banana monkey

var program_name = process.argv[0]; //value will be "node"
var script_path = process.argv[1]; //value will be "yourscript.js"
var first_value = process.argv[2]; //value will be "banana"
var second_value = process.argv[3]; //value will be "monkey"

  • 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:

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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, mandatory: true},
    'ooo': {key: 'o'}
});

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If you run the previous code with this command:

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node <your_script.js> -c 23 45 --map -k 23 file1 file2

Then ops object will be as follows:

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

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

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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 we call ops.printHelp() we will get the following:

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USAGE: node something.js [--check <ARG1> <ARG2>] [--kaka] [--ooo] [--map]
  -c, --check <ARG1> <ARG2>   What this option means (mandatory)
  -k, --kaka                  (mandatory)
  --map                       Another description
  -o, --ooo

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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:

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npm install stdio

  • If your script is myScript.js and you want to pass the first and last name, ‘Wiki Techy’, as arguments like below:
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node myScript.js Wiki Techy

Then your script is written as follows:

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var firstName = process.argv[2]; // Will be set to ‘Wiki'
var lastName = process.argv[3]; // Will be set to ‘Techy'

  • Here is an another solution:
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#!/usr/bin/env node
var argv = require('yargs').argv;
console.log('(%d,%d)', argv.x, argv.y);
console.log(argv._);

Output is here (it reads options with dashes etc, short and long, numeric etc).

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$ ./nonopt.js -x 6.82 -y 3.35 rum
(6.82,3.35)
[ 'rum' ] 
$ ./nonopt.js "me hearties" -x 0.54 yo -y 1.12 ho
(0.54,1.12)
[ 'me hearties', 'yo', 'ho' ]

  • we can parse all arguments and check if they exist.

file: parse-cli-arguments.js:

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module.exports = function(requiredArguments){
    var arguments = {};

    for (var index = 0; index < process.argv.length; index++) {
        var re = new RegExp('--([A-Za-z0-9_]+)=([A/-Za-z0-9_]+)'),
            matches = re.exec(process.argv[index]);

        if(matches !== null) {
            arguments[matches[1]] = matches[2];
        }
    }
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for (var index = 0; index < requiredArguments.length; index++) {
        if (arguments[requiredArguments[index]] === undefined) {
            throw(requiredArguments[index] + ' not defined. Please add the argument with --' + requiredArguments[index]);
        }
    }

    return arguments;
}

Than just do:

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var arguments = require('./parse-cli-arguments')(['foo', 'bar', 'xpto']);

  • npm install ps-grab

If we want to run something like this :

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node greeting.js --user Wikitechy --website http://www.wikitechy.com
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var grab=require('ps-grab');
grab('--username') // return ‘Wikitechy'
grab('--action') // return 'http://www.wikitechy.com'

Or something like :

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node vbox.js -OS redhat -VM template-12332 ;
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var grab=require('ps-grab');
grab('-OS') // return 'redhat'
grab('-VM') // return 'template-12332

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