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     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

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whithout librairies  using Array prototype reduce    const args   process argv slice 2  reduce  acc  arg    gt         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  amp  Number  console log args       count  2  print  true  debug  false  msg   hi

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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

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as stated in the node docs  The process argv property returns an array containing the command line arguments passed when the Node js process was launched   For example  assuming the following script for process-args js      print process argv process argv forEach  val  index    gt       console log    index     val           Launching the Node js process as      node process-args js one two three four   Would generate the output   0   usr local bin node 1   Users mjr work node process-args js 2  one 3  two three 4  four

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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

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Here s my 0-dep solution for named arguments   const args   process argv      slice 2       map arg   gt  arg split            reduce  args   value  key     gt            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

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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    gt           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

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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

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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

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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

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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

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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   gt       let object           let  regexForProp  regexForVal          gt   new RegExp             new RegExp                     let  prop  value          gt   regexForProp exec val   regexForVal exec val            if  prop         object val    true        return object        else         object prop 1     value 1          return object               reduce  obj  item    gt        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

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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  lt  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  lt  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

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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

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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        gt          map process argv   arg    gt            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

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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

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Parsing argument based on standard input   --key value   const argv         gt        const arguments           process argv slice 2  map   element    gt            const matches   element match   --  a-zA-Z0-9                    if   matches                arguments matches 1     matches 2                   replace      quot         replace     quot                                 return arguments         Command example node app js --name stackoverflow --id 10 another-argument --text  quot Hello World quot   Result of argv  console log argv        name   quot stackoverflow quot       id   quot 10 quot       text   quot Hello World quot

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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

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No Libs with Flags Formatted into a Simple Object function getArgs          const args           process argv          slice 2  process argv length           forEach  arg   gt               long arg         if  arg slice 0 2       --                 const longArg   arg split                   const longArgFlag   longArg 0  slice 2 longArg 0  length               const longArgValue   longArg length  gt  1   longArg 1    true              args longArgFlag    longArgValue                       flags         else if  arg 0       -                 const flags   arg slice 1 arg length  split                  flags forEach flag   gt                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

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I extended the getArgs function just to get also commands  as well as flags  -f  --anotherflag  and named args  --data blablabla    The module          module getArgs js    get command line arguments  commands  named arguments  flags         see https   stackoverflow com a 54098693 1786393        return  Object         function getArgs        const commands        const args        process argv      slice 2  process argv length       forEach  arg   gt             long arg       if  arg slice 0 2       --             const longArg   arg split              const longArgFlag   longArg 0  slice 2 longArg 0  length          const longArgValue   longArg length  gt  1   longArg 1    true         args longArgFlag    longArgValue                flags       else if  arg 0       -             const flags   arg slice 1 arg length  split             flags forEach flag   gt              args flag    true                         else            commands       commands push arg                   return   args  commands          test if  require main     module         node getArgs test --dir examples getUserName --start getUserName askName   console log  getArgs        module exports     getArgs      Usage example     node lib getArgs test --dir examples getUserName --start getUserName askName     args    dir   examples getUserName   start   getUserName askName       commands     test         node lib getArgs --dir examples getUserName --start getUserName askName test tutorial     args    dir   examples getUserName   start   getUserName askName       commands     test    tutorial

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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

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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   gt        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

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ES6-style no-dependencies solution  const longArgs   arg   gt        const   key  value     arg split           return    key slice 2    value    true       const flags   arg   gt      arg slice 1   reduce  flagObj  f    gt        flagObj   f   true            const args        gt      process argv          slice 2           reduce  args  arg    gt                    args                   arg startsWith  --    amp  amp  longArgs arg       arg 0       -   amp  amp  flags arg                      console log args

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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  lt  process argv length  j            console log j     - gt       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

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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  lt command gt   options    For example     git commit --squash -m  This is my commit message    Command and sub-command syntax  docker style  in the form     executable  lt command gt   options   lt sub-command gt   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

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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

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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

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proj js for var i 0 i lt process argv length i       console log process argv i       Terminal  nodemon app js  quot arg1 quot   quot arg2 quot   quot arg3 quot   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   The directory of node exe in your machine  C  Program Files nodejs node exe  The directory of your project file  proj js  Your first argument to node   arg1  Your second argument to node  arg2  Your third argument to node   arg3    your actual arguments start form second index of argv array  that is process argv 2

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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  lt your script js gt  -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  amp  amp  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  lt ARG1 gt   lt ARG2 gt    --kaka   --ooo   --map    -c  --check  lt ARG1 gt   lt ARG2 gt    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

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A simple snippet if any need it   var fs   require  fs    objMod        process argv slice 2  map function y  i      y   y split         if  y 0   amp  amp  y 1   objMod y 0     y 1     else console log  Error in argument number      i 1

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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

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process argv is your friend  capturing command line args is natively supported in Node JS  See example below    process argv forEach  val  index    gt      console log    index     val

[javascript] How do I pass command line arguments to a Node.js program?

whithout librairies: using Array.prototype.reduce()

also,

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