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

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

Standard Method (no library)

The arguments are stored in process.argv

Here are the node docs on handling command line args:

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.

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

This will generate:

$ 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 

Answer 2

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 3

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 4

2018 answer based on current trends in the wild:

---

Vanilla javascript argument parsing:

const args = process.argv; console.log(args); 

This returns:

$ node server.js one two=three four ['node', '/home/server.js', 'one', 'two=three', 'four'] 

Official docs

---

Most used NPM packages for argument parsing:

Minimist: For minimal argument parsing.

Commander.js: Most adopted module for argument parsing.

Meow: Lighter alternative to Commander.js

Yargs: More sophisticated argument parsing (heavy).

Vorpal.js: Mature / interactive command-line applications with argument parsing.

Answer 5

No Libs with Flags Formatted into a Simple Object

const getArgs = () => process.argv.reduce((args, arg) => { // long arg if (arg.slice(0, 2) === "--") { const longArg = arg.split("="); const longArgFlag = longArg[0].slice(2); const longArgValue = longArg.length > 1 ? longArg[1] : true; args[longArgFlag] = longArgValue; } // flags else if (arg[0] === "-") { const flags = arg.slice(1).split(""); flags.forEach((flag) => { args[flag] = true; }); } return args; }, {}); const args = getArgs(); console.log(args); 

Examples

Simple

input

node test.js -D --name=Hello 

output

{ D: true, name: 'Hello' } 

Real World

input

node config/build.js -lHRs --ip=$HOST --port=$PORT --env=dev 

output

{ l: true, H: true, R: true, s: true, ip: '127.0.0.1', port: '8080', env: 'dev' } 

Answer 6

Optimist (node-optimist)

Check out optimist library, it is much better than parsing command line options by hand.

Update

Optimist is deprecated. Try yargs which is an active fork of optimist.

Answer 7

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 8

Commander.js

Works great for defining your options, actions, and arguments. It also generates the help pages for you.

Promptly

Works great for getting input from the user, if you like the callback approach.

Co-Prompt

Works great for getting input from the user, if you like the generator approach.

Answer 9

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 <your_script.js> -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 <ARG1> <ARG2>] [--kaka] [--ooo] [--map] -c, --check <ARG1> <ARG2> 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 

Answer 10

If your script is called myScript.js and you want to pass the first and last name, 'Sean Worthington', as arguments like below:

node myScript.js Sean Worthington 

Then within your script you write:

var firstName = process.argv[2]; // Will be set to 'Sean' var lastName = process.argv[3]; // Will be set to 'Worthington' 

Answer 11

Simple + ES6 + no-dependency + supports boolean flags

const process = require( 'process' ); const argv = key => { // Return true if the key exists and a value is undefined if ( process.argv.includes( `--${ key }` ) ) return true; const value = process.argv.find( element => element.startsWith( `--${ key }=` ) ); // Return null if the key does not exist and a value is undefined if ( !value ) return null; return value.replace( `--${ key }=` , '' ); } 

Output:

• If invoked with node app.js then argv('foo') will return null
• If invoked with node app.js --foo then argv('foo') will return true
• If invoked with node app.js --foo= then argv('foo') will return ''
• If invoked with node app.js --foo=bar then argv('foo') will return 'bar'

Answer 12

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 13

Here's my 0-dep solution for named arguments:

const args = process.argv .slice(2) .map(arg => arg.split('=')) .reduce((args, [value, key]) => { args[value] = key; return args; }, {}); console.log(args.foo) console.log(args.fizz) 

Example:

$ node test.js foo=bar fizz=buzz bar buzz 

Note: Naturally this will fail when the argument contains a =. This is only for very simple usage.

Answer 14

Native Method

Nodejs team added util.parseArgs function in versions 18.3.0 and 16.17.0. So if you use these or higher versions of nodejs you can parse command line arguments with this native solution. parseArgs was experimental up to v18 and is stable from v20.

An example of usage from the documentation:

const {parseArgs} = require('node:util'); const args = process.argv; const options = { foo: { type: 'boolean', short: 'f' }, bar: { type: 'string' } }; const { values, positionals } = parseArgs({ args, options, allowPositionals: true }); console.log(values); console.log(positionals); 

Output sample:

$ node parseargs.js -f --bar b [Object: null prototype] { foo: true, bar: 'b' } [ '/Users/mbelsky/.nvm/versions/node/v18.12.1/bin/node', '/Users/mbelsky/parseargs.js' ] 

Answer 15

There's an app for that. Well, module. Well, more than one, probably hundreds.

Yargs is one of the fun ones, its docs are cool to read.

Here's an example from the github/npm page:

#!/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).

$ ./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' ] 

Answer 16

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 machine (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 second index of argv array, that is process.argv[2].

Answer 17

whithout librairies: using Array.prototype.reduce()

const args = process.argv.slice(2).reduce((acc, arg) => { let [k, v = true] = arg.split('=') acc[k] = v return acc }, {}) 

for this command node index.js count=2 print debug=false msg=hi

console.log(args) // { count: '2', print: true, debug: 'false', msg: 'hi' } 

also,

we can change

 let [k, v = true] = arg.split('=') acc[k] = v 

by (much longer)

 let [k, v] = arg.split('=') acc[k] = v === undefined ? true : /true|false/.test(v) ? v === 'true' : /[\d|\.]+/.test(v) ? Number(v) : v 

to auto parse Boolean & Number

console.log(args) // { count: 2, print: true, debug: false, msg: 'hi' } 

Answer 18

Parsing argument based on standard input ( --key=value )

const argv = (() => { const arguments = {}; process.argv.slice(2).map( (element) => { const matches = element.match( '--([a-zA-Z0-9]+)=(.*)'); if ( matches ){ arguments[matches[1]] = matches[2] .replace(/^['"]/, '').replace(/['"]$/, ''); } }); return arguments; })(); 

Command example

node app.js --name=stackoverflow --id=10 another-argument --text="Hello World" 

Result of argv: console.log(argv)

{ name: "stackoverflow", id: "10", text: "Hello World" } 

Answer 19

In the node code require the built in process lib.

const {argv} = require('process') 

Run the program with their arguments.

$ node process-args.js one two=three four 

argv is the array that follows:

argv[0] = /usr/bin/node argv[1] = /home/user/process-args.js argv[2] = one argv[3] = two=three argv[4] = four 

Answer 20

Passing,parsing arguments is an easy process. Node provides you with the process.argv property, which is an array of strings, which are the arguments that were used when Node was invoked. The first entry of the array is the Node executable, and the second entry is the name of your script.

If you run script with below atguments

$ node args.js arg1 arg2 

File : args.js

console.log(process.argv) 

You will get array like

 ['node','args.js','arg1','arg2'] 

Answer 21

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 22

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 23

Solution using Set to solve the position issue if using simple args (without key+values).

For example both commands will return same result:

node server.js detail json node server.js json detail 

const args = new Set(process.argv.slice(2)); 

Then one can use args.has('detail') or args.has('json') without worrying about position.

Answer 24

You can reach command line arguments using system.args. And i use the solution below to parse arguments into an object, so i can get which one i want by name.

var system = require('system'); var args = {}; system.args.map(function(x){return x.split("=")}) .map(function(y){args[y[0]]=y[1]}); 

now you don't need to know the index of the argument. use it like args.whatever

Note: you should use named arguments like file.js x=1 y=2 to use this solution.

Answer 25

Passing arguments is easy, and receiving them is just a matter of reading the process.argv array Node makes accessible from everywhere, basically. But you're sure to want to read them as key/value pairs, so you'll need a piece to script to interpret it.

Joseph Merdrignac posted a beautiful one using reduce, but it relied on a key=value syntax instead of -k value and --key value. I rewrote it much uglier and longer to use that second standard, and I'll post it as an answer because it wouldn't fit as a commentary. But it does get the job done.

 const args = process.argv.slice(2).reduce((acc,arg,cur,arr)=>{ if(arg.match(/^--/)){ acc[arg.substring(2)] = true acc['_lastkey'] = arg.substring(2) } else if(arg.match(/^-[^-]/)){ for(key of arg.substring(1).split('')){ acc[key] = true acc['_lastkey'] = key } } else if(acc['_lastkey']){ acc[acc['_lastkey']] = arg delete acc['_lastkey'] } else acc[arg] = true if(cur==arr.length-1) delete acc['_lastkey'] return acc },{}) 

With this code a command node script.js alpha beta -charlie delta --echo foxtrot would give you the following object

 args = { "alpha":true, "beta":true, "c":true, "h":true, "a":true, "r":true "l":true, "i":true, "e":"delta", "echo":"foxtrot" } 

Answer 26

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.

Answer 27

TypeScript solution with no libraries:

interface IParams { [key: string]: string } function parseCliParams(): IParams { const args: IParams = {}; const rawArgs = process.argv.slice(2, process.argv.length); rawArgs.forEach((arg: string, index) => { // Long arguments with '--' flags: if (arg.slice(0, 2).includes('--')) { const longArgKey = arg.slice(2, arg.length); const longArgValue = rawArgs[index + 1]; // Next value, e.g.: --connection connection_name args[longArgKey] = longArgValue; } // Shot arguments with '-' flags: else if (arg.slice(0, 1).includes('-')) { const longArgKey = arg.slice(1, arg.length); const longArgValue = rawArgs[index + 1]; // Next value, e.g.: -c connection_name args[longArgKey] = longArgValue; } }); return args; } const params = parseCliParams(); console.log('params: ', params); 

Input: ts-node index.js -p param --parameter parameter

Output: { p: 'param ', parameter: 'parameter' }

Answer 28

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 29

The simplest way of retrieving arguments in Node.js is via the process.argv array. This is a global object that you can use without importing any additional libraries to use it. You simply need to pass arguments to a Node.js application, just like we showed earlier, and these arguments can be accessed within the application via the process.argv array.

The first element of the process.argv array will always be a file system path pointing to the node executable. The second element is the name of the JavaScript file that is being executed. And the third element is the first argument that was actually passed by the user.

'use strict'; for (let j = 0; j < process.argv.length; j++) { console.log(j + ' -> ' + (process.argv[j])); } 

All this script does is loop through the process.argv array and prints the indexes, along with the elements stored in those indexes. It's very useful for debugging if you ever question what arguments you're receiving, and in what order.

You can also use libraries like yargs for working with commnadline arguments.

Answer 30

ES6-style no-dependencies solution:

const longArgs = arg => { const [ key, value ] = arg.split('='); return { [key.slice(2)]: value || true } }; const flags = arg => [...arg.slice(1)].reduce((flagObj, f) => ({ ...flagObj, [f]: true }), {}); const args = () => process.argv .slice(2) .reduce((args, arg) => ({ ...args, ...((arg.startsWith('--') && longArgs(arg)) || (arg[0] === '-' && flags(arg))) }), {}); console.log(args());