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

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:

$ node server.js folder

here server.js is my server code. Node.js help says this is possible:

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

How would I access those arguments in JavaScript? Somehow I was not able to find this information on the web.

Answer 1

npm install ps-grab

If you want to run something like this :

node greeting.js --user Abdennour --website http://abdennoor.com 

--

var grab=require('ps-grab');
grab('--username') // return 'Abdennour'
grab('--action') // return 'http://abdennoor.com'

---

Or something like :

node vbox.js -OS redhat -VM template-12332 ;

--

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

Answer 2

The up-to-date right answer for this it to use the minimist library. We used to use node-optimist but it has since been deprecated.

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

var argv = require('minimist')(process.argv.slice(2));
console.dir(argv);

-

$ node example/parse.js -a beep -b boop
{ _: [], a: 'beep', b: 'boop' }

-

$ 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' }

Answer 3

To normalize the arguments like a regular javascript function would receive, I do this in my node.js shell scripts:

var args = process.argv.slice(2);

Note that the first arg is usually the path to nodejs, and the second arg is the location of the script you're executing.

Answer 4

Several great answers here, but it all seems very complex. This is very similar to how bash scripts access argument values and it's already provided standard with node.js as MooGoo pointed out. (Just to make it understandable to somebody that's new to node.js)

Example:

$ 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"

Answer 5

Most of the people have given good answers. I would also like to contribute something here. I am providing the answer using lodash library to iterate through all command line arguments we pass while starting the app:

// Lodash library
const _ = require('lodash');

// Function that goes through each CommandLine Arguments and prints it to the console.
const runApp = () => {
    _.map(process.argv, (arg) => {
        console.log(arg);
    });
};

// Calling the function.
runApp();

To run above code just run following commands:

npm install
node index.js xyz abc 123 456

The result will be:

xyz 
abc 
123
456

Answer 6

Although Above answers are perfect, and someone has already suggested yargs, using the package is really easy. This is a nice package which makes passing arguments to command line really easy.

npm i yargs
const yargs = require("yargs");
const argv = yargs.argv;
console.log(argv);

Please visit https://yargs.js.org/ for more info.