Run function in script from command line Node JS

Question

I m writing a web app in Node  If I ve got some JS file db js with a function init in it how could I call that function from the command line

User · Answer

Sometimes you want to run a function via CLI  sometimes you want to require it from another module  Here s how to do both      file to run const runMe        gt     if  require main     module      runMe      module exports   runMe

User · Answer

If your file just contains your function  for example   myFile js   function myMethod someVariable        console log someVariable      Calling it from the command line like this nothing will happen   node myFile js   But if you change your file   myFile js   myMethod  Hello World     function myMethod someVariable        console log someVariable      Now this will work from the command line   node myFile js

User · Answer

If you turn db js into a module you can require it from db init js and just  node db init js   db js   module exports       method1  function               method2  function                db init js   var db   require    db     db method1    db method2

User · Answer

maybe this method is not what you mean  but who knows it can help index js const arg   process argv splice 2    function printToCli text       console log text     switch arg 0        case  quot --run quot           printToCli  quot how are you quot       break      default  console log  quot use --run flag quot       and run command node   --run command line probuss-MacBook-Air fb v8 probus  node   --run how are you probuss-MacBook-Air fb v8 probus    and you can add more arg 0    arg 1   arg 2      and more for node   --run -myarg1 -myarg2

User · Answer

As per the other answers  add the following to someFile js  module exports someFunction   function        console log  hi         You can then add the following to package json   scripts         myScript    node -e  require     someFile    someFunction         From the terminal  you can then call  npm run myScript   I find this a much easier way to remember the commands and use them

User · Answer

This one is dirty but works     I will be calling main   function from my script  Previously I just put calls to main at the end of script  However I did add some other functions and exported them from script  to use functions in some other parts of code  - but I dont want to execute main   function every time I import other functions in other scripts    So I did this  in my script i removed call to main    and instead at the end of script I put this check   if  process argv includes  main         main        So when I want to call that function in CLI  node src myScript js main

User · Answer

No comment on why you want to do this  or what might be a more standard practice  here is a solution to your question     Keep in mind that the type of quotes required by your command line may vary    In your db js  export the init function  There are many ways  but for example   module exports init   function        console log  hi         Then call it like this  assuming your db js is in the same directory as your command prompt   node -e  require    db   init      To other readers  the OP s  init function could have been called anything  it is not important  it is just the specific name used in the question

User · Answer

Try make-runnable   In db js  add require  make-runnable    to the end   Now you can do   node db js init   Any further args would get passed to the init method

User · Answer

simple way   let s say you have db js file in a helpers directory in project structure   now go inside helpers directory and go to node console   helpers   node   2  require db js file   gt  var db   require    db     3  call your function  in your case its init      gt  db init     hope this helps

User · Answer

I do a IIFE  something like that         gt  init         this code will be executed immediately and invoke the init function

User · Answer

Update 2020 - CLI As  mix3d pointed out you can just run a command where file js is your file and someFunction is your function optionally followed by parameters separated with spaces npx run-func file js someFunction  quot just some parameter quot   That s it  file js called in the example above const someFunction    param    gt  console log  Welcome  your param is   param      exporting is crucial module exports     someFunction    More detailed description Run directly from CLI  global  Install npm i -g run-func  Usage i e  run function  quot init quot   it must be exported  see the bottom run-func db js init  or Run from package json script  local  Install npm i -S run-func  Setup  quot scripts quot         quot init quot    quot run-func db js init quot     Usage npm run init  Params Any following arguments will be passed as function parameters init param1  param2  run-func db js init param1 param2  Important the function  in this example init  must be exported in the file containing it module exports     init     or ES6 export export   init

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