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 + \         


        

Answer 1

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.

Answer 2

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);

Answer 3

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')()

Answer 4

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("./standard_funcs.js")

// use -------------------------------------------

var x = sf.add(4,2);
console.log(x);

var y = sf.subtract(4,2);
console.log(y);

    

output

6
2

Answer 5

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 :)

Answer 6

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 () 
{
};