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

command-line-args is worth a look!

You can set options using the main notation standards (learn more). These commands are all equivalent, setting the same values:

$ example --verbose --timeout=1000 --src one.js --src two.js
$ example --verbose --timeout 1000 --src one.js two.js
$ example -vt 1000 --src one.js two.js
$ example -vt 1000 one.js two.js

To access the values, first create a list of option definitions describing the options your application accepts. The type property is a setter function (the value supplied is passed through this), giving you full control over the value received.

const optionDefinitions = [
  { name: 'verbose', alias: 'v', type: Boolean },
  { name: 'src', type: String, multiple: true, defaultOption: true },
  { name: 'timeout', alias: 't', type: Number }
]

Next, parse the options using commandLineArgs():

const commandLineArgs = require('command-line-args')
const options = commandLineArgs(optionDefinitions)

options now looks like this:

{
  src: [
    'one.js',
    'two.js'
  ],
  verbose: true,
  timeout: 1000
}

Advanced usage

Beside the above typical usage, you can configure command-line-args to accept more advanced syntax forms.

Command-based syntax (git style) in the form:

$ executable  [options]

For example.

$ git commit --squash -m "This is my commit message"

Command and sub-command syntax (docker style) in the form:

$ executable  [options]  [options]

For example.

$ docker run --detached --image centos bash -c yum install -y httpd

Usage guide generation

A usage guide (typically printed when --help is set) can be generated using command-line-usage. See the examples below and read the documentation for instructions how to create them.

A typical usage guide example.

The polymer-cli usage guide is a good real-life example.

Further Reading

There is plenty more to learn, please see the wiki for examples and documentation.