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

You can parse all arguments and check if they exist.

file: parse-cli-arguments.js:

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];
        }
    }

    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:

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

Answer 2

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 3

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 4

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 <command> [options]

For example.

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

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

$ executable <command> [options] <sub-command> [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.

Answer 5

Without libraries

If you want to do this in vanilla JS/ES6 you can use the following solution

worked only in NodeJS > 6

const args = process.argv
  .slice(2)
  .map((val, i)=>{
    let object = {};
    let [regexForProp, regexForVal] = (() => [new RegExp('^(.+?)='), new RegExp('\=(.*)')] )();
    let [prop, value] = (() => [regexForProp.exec(val), regexForVal.exec(val)] )();
    if(!prop){
      object[val] = true;
      return object;
    } else {
      object[prop[1]] = value[1] ;
      return object
    }
  })
  .reduce((obj, item) => {
    let prop = Object.keys(item)[0];
    obj[prop] = item[prop];
    return obj;
  }, {});

And this command

node index.js host=http://google.com port=8080 production

will produce the following result

console.log(args);//{ host:'http://google.com',port:'8080',production:true }
console.log(args.host);//http://google.com
console.log(args.port);//8080
console.log(args.production);//true

p.s. Please correct the code in map and reduce function if you find more elegant solution, thanks ;)

Answer 6

proj.js

for(var i=0;i<process.argv.length;i++){
  console.log(process.argv[i]);
}

Terminal:

nodemon app.js "arg1" "arg2" "arg3"

Result:

0 'C:\\Program Files\\nodejs\\node.exe'
1 'C:\\Users\\Nouman\\Desktop\\Node\\camer nodejs\\proj.js'
2 'arg1' your first argument you passed.
3 'arg2' your second argument you passed.
4 'arg3' your third argument you passed.

Explaination:

0 : The directory of node.exe in your maching (C:\Program Files\nodejs\node.exe')

1 : The directory of your project file. (proj.js)

2 : Your first argument to node (arg1)

3 : Your second argument to node (arg2)

4 : Your third argument to node (arg3)

your actual arguments start form 2nd index of argv array, that is process.argv[2].