In Node js how do I include functions from my other files

Question

Let s say I have a file called app js  Pretty simple   var express   require  express    var app   express createServer    app set  views     dirname     views    app set  view engine    ejs    app get      function req  res     res render  index    locals        title   NowJS   Express Example              app listen 8080     What if I have a functions inside  tools js    How would I import them to use in apps js   Or   am I supposed to turn  tools  into a module  and then require it   lt  lt  seems hard  I rather do the basic import of the tools js file

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Here is a plain and simple explanation   Server js content      Include the public functions from  helpers js  var helpers   require    helpers        Let s assume this is the data which comes from the database or somewhere else var databaseName    Walter   var databaseSurname    Heisenberg       Use the function from  helpers js  in the main file  which is server js var fullname   helpers concatenateNames databaseName  databaseSurname     Helpers js content       module exports  is a node JS specific feature  it does not work with regular JavaScript module exports           This is the function which will be called in the main file  which is server js      The parameters  name  and  surname  will be provided inside the function      when the function is called in the main file       Example  concatenameNames  John  Doe      concatenateNames  function  name  surname            var wholeName   name         surname        return wholeName          sampleFunctionTwo  function                     Private variables and functions which will not be accessible outside this file var privateFunction   function

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Udo G  said          The eval   can t be used inside a function and must be called inside   the global scope otherwise no functions or variables will be   accessible  i e  you can t create a include   utility function or   something like that        He s right  but there s a way to affect the global scope from a function  Improving his example   function include file         with  global            eval fs readFileSync file                     include  somefile with some declarations js        the declarations are now accessible here    Hope  that helps

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Another way to do this in my opinion  is to execute everything in the lib file when you call require   function using  function    things here           doing this will make all these functions global scope  exactly like the eval   solution  src lib js   function          funcOne   function                 console log  mlt funcOne here               funcThree   function firstName                console log firstName   calls funcThree here               name    Mulatinho       myobject                 title   Node JS is cool               funcFour  function                         return console log  internal funcFour   called here                                And then in your main code you can call your functions by name like   main js  require    src lib   funcOne    funcThree  Alex    console log name   console log myobject   console log myobject funcFour       Will make this output  bash-3 2  node -v v7 2 1 bash-3 2  node main js  mlt funcOne here Alex calls funcThree here Mulatinho   title   Node JS is cool   funcFour   Function  funcFour    internal funcFour   called here undefined   Pay atention to the undefined when you call my object funcFour    it will be the same if you load with eval    Hope it helps

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To turn  tools  into a module  I don t see hard at all  Despite all the other answers I would still recommend use of module exports     util js module exports        myFunction  function            your logic in here    let message    I am message from myFunction      return message           Now we need to assign this exports to global scope  in your app index server js     var util   require    util      Now you can refer and call function  as     util myFunction    console log util myFunction        prints in console  I am message from myFunction

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create two files e g standard funcs js and main js 1   standard funcs js    Declaration --------------------------------------   module exports             add       subtract                       Implementation ----------------------------------   function add x  y        return x   y       function subtract x  y        return x - y                   2   main js    include ---------------------------------------  const sf  require  quot   standard funcs js quot       use -------------------------------------------  var x   sf add 4 2   console log x    var y   sf subtract 4 2   console log y          output 6 2

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Another method when using node js and express js framework  var f1   function       console log  f1      var f2   function       console log  f2       module exports        f1   f1     f2   f2     store this in a js file named s and in the folder statics  Now to use the function  var s   require     statics s    s f1    s f2

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I just want to add  in case you need just certain functions imported from your tools js  then you can use a destructuring assignment which is supported in node js since version 6 4 - see node green     Example   both files are in the same folder      tools js   module exports         sum  function a b            return a   b             isEven  function a            return a   2    0                main js   const   isEven     require    tools js     console log isEven 10      output  true    This also avoids that you assign those functions as properties of another object as its the case in the following  common  assignment   const tools   require    tools js      where you need to call tools isEven 10      NOTE   Don t forget to prefix your file name with the correct path - even if both files are in the same folder  you need to prefix with     From Node js docs      Without a leading            or       to indicate a file  the module   must either be a core module or is loaded from a node modules folder

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This is the best way i have created so far   var fs   require  fs        includedFiles         global include   function  fileName      var sys   require  sys      sys puts  Loading file      fileName     var ev   require fileName     for  var prop in ev        global prop    ev prop         includedFiles  fileName    true      global includeOnce   function  fileName      if   includedFiles  fileName         include fileName           global includeFolderOnce   function  folder      var file  fileName        sys   require  sys          files   fs readdirSync folder      var getFileName   function str            var splited   str split               splited pop            return splited join                      getExtension   function str            var splited   str split               return splited splited length - 1               for  var i   0  i  lt  files length  i          file   files i       if  getExtension file       js           fileName   getFileName file         try           includeOnce folder         file           catch  err               if  ext vars                 console log ext vars dump err                 else           sys puts err                                      includeFolderOnce    extensions    includeOnce    bin Lara js     var lara   new Lara      You still need to inform what you want to export  includeOnce    bin WebServer js     function Lara       this webServer   new WebServer      this webServer start       Lara prototype webServer   null   module exports Lara   Lara

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You can put your functions in global variables  but it s better practice to just turn your tools script into a module  It s really not too hard     just attach your public API to the exports object  Take a look at Understanding Node js  exports module for some more detail

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say we wants to call function ping   and add 30 20  which is in lib js file  from main js   main js  lib   require    lib js    output   lib ping    console log output      Passing Parameters console log  Sum of A and B       lib add 20 30       lib js  this ping function          return   Ping Success          Functions with parameters this add function a b                return a b

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It worked with me like the following       Lib1 js    Any other private code here      Code you want to export exports function1   function params             exports function2   function params                 Again any private code   now in the Main js file you need to include Lib1 js  var mylib   requires  lib1 js    mylib function1 params   mylib function2 params     Please remember to put the Lib1 js in node modules folder

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You can require any js file  you just need to declare what you want to expose      tools js             module exports       foo  function             whatever        bar  function             whatever         var zemba   function          And in your app file      app js           var tools   require    tools    console log typeof tools foo        gt   function  console log typeof tools bar        gt   function  console log typeof tools zemba        gt  undefined

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Use   var mymodule   require    tools js     app js   module exports  lt your function gt    function           lt what should the function do gt

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I was as well searching for an option to include code without writing modules  resp  use the same tested standalone sources from a different project for a Node js service - and jmparattes answer did it for me   The benefit is  you don t pollute the namespace  I don t have trouble with  use strict   and it works well   Here a full sample   Script to load -  lib foo js   use strict     function         var Foo   function e           this foo   e             Foo prototype x   1       return Foo          SampleModule - index js   use strict    const fs   require  fs    const path   require  path     var SampleModule   module exports          instAFoo  function            var Foo   eval apply              this   fs readFileSync path join   dirname    lib foo js    toString                       var instance   new Foo  bar            console log instance foo       bar          console log instance x       1             Hope this was helpfull somehow

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Create two js files     File cal js module exports         sum  function a b            return a b            multiply  function a b            return a b            Main js file     File app js var tools   require    cal js    var value   tools sum 10 20   console log  Value    value     Console Output  Value  30

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Include file and run it in given  non-global  context  fileToInclude js  define        data    XYZ        main js  var fs   require  fs    var vm   require  vm     function include path  context        var code   fs readFileSync path   utf-8        vm runInContext code  vm createContext context           Include file  var customContext          define   function  data            console log data            include    fileToInclude js   customContext

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You can simple just require    filename     Eg      file  index js var express   require  express    var app   express    var child   require    child    app use   child   child   app get      function  req  res      res send  parent        app listen process env PORT  function        console log  Example app listening on port   process env PORT                file  child js var express   require  express    child   express Router    console log  child    child get   child   function req  res     res send  Child2        child get      function req  res     res send  Child         module exports   child    Please note that    you can t listen PORT on the child file  only parent express module has PORT listener Child is using  Router   not parent Express moudle

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If  despite all the other answers  you still want to traditionally include a file in a node js source file  you can use this   var fs   require  fs        file is included here  eval fs readFileSync  tools js           The empty string concatenation     is necessary to get the file content as a string and not an object  you can also use  toString   if you prefer   The eval   can t be used inside a function and must be called inside the global scope otherwise no functions or variables will be accessible  i e  you can t create a include   utility function or something like that     Please note that in most cases this is bad practice and you should instead write a module  However  there are rare situations  where pollution of your local context namespace is what you really want   Update 2015-08-06  Please also note this won t work with  use strict    when you are in  strict mode   because functions and variables defined in the  imported  file can t be accessed by the code that does the import  Strict mode enforces some rules defined by newer versions of the language standard  This may be another reason to avoid the solution described here

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app js  let   func name     require  path to tools js    func name         function calling   tools js  let func name   function                   function body             module exports     func name

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I was also looking for a NodeJS  include  function and I checked the solution proposed by Udo G - see message https   stackoverflow com a 8744519 2979590  His code doesn t work with my included JS files  Finally I solved the problem like that   var fs   require  fs     function read f      return fs readFileSync f  toString      function include f      eval apply global   read f        include  somefile with some declarations js      Sure  that helps

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You need no new functions nor new modules  You simply need to execute the module you re calling if you don t want to use namespace  in tools js module exports   function          this sum   function a b    return a b        this multiply   function a b    return a b          etc    in app js or in any other  js like myController js   instead of var tools   require  tools js   which force us to use a namespace and call tools like tools sum 1 2   we can simply call require  tools js       and then sum 1 2    in my case I have a file with controllers ctrls js module exports   function         this Categories   require  categories js       and I can use Categories in every context as public class after require  ctrls js

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The vm module in Node js provides the ability to execute JavaScript code within the current context  including global object    See http   nodejs org docs latest api vm html vm vm runinthiscontext code filename  Note that  as of today  there s a bug in the vm module that prevenst runInThisContext from doing the right when invoked from a new context   This only matters if your main program executes code within a new context and then that code calls runInThisContext   See https   github com joyent node issues 898  Sadly  the with global  approach that Fernando suggested doesn t work for named functions like  function foo        In short  here s an include   function that works for me   function include path        var code   fs readFileSync path   utf-8        vm runInThisContext code  path

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create two files e g app js and tools js  app js  const tools  require    tools js     var x   tools add 4 2     var y   tools subtract 4 2     console log x   console log y     tools js   const add   function x  y           return x y         const subtract   function x  y               return x-y             module exports            add subtract         output  6 2

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Like you are having a file abc txt and many more    Create 2 files  fileread js and fetchingfile js  then in fileread js write this code   function fileread filename        var contents  fs readFileSync filename           return contents             var fs   require  fs        file system        var data   fileread  abc txt        module exports fileread   fileread        data say          console log data toString         In fetchingfile js write this code   function myerror        console log  Hey need some help        console log  type file abc txt       var ags   require  minimist   process argv slice 2     string   file      if ags help     ags file        myerror        process exit 1     var hello   require    fileread js    var data   hello fileread ags file       importing module here  console log data toString       Now  in a terminal        node fetchingfile js --file abc txt  You are passing the file name as an argument  moreover include all files in readfile js instead of passing it   Thanks

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