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

If you'd like to take advantage of multiple CPUs & Microservice architecture, to speed things up...Use RPCs over forked processes.

Sounds complex, but it's simple if you use octopus.

Here's an example:

on tools.js add :

const octopus = require('octopus');
var rpc = new octopus('tools:tool1');

rpc.over(process, 'processRemote');

var sum = rpc.command('sum'); // This is the example tool.js function to make available in app.js

sum.provide(function (data) { // This is the function body
    return data.a + data.b;
});

on app.js, add :

const { fork } = require('child_process');
const octopus = require('octopus');
const toolprocess = fork('tools.js');

var rpc = new octopus('parent:parent1');
rpc.over(toolprocess, 'processRemote');

var sum = rpc.command('sum');

// Calling the tool.js sum function from app.js
sum.call('tools:*', {
    a:2, 
    b:3
})
.then((res)=>console.log('response : ',rpc.parseResponses(res)[0].response));

disclosure - I am the author of octopus, and built if for a similar usecase of mine, since i couldn't find any lightweight libraries.

Answer 2

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 

Answer 3

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:

1. you can't listen PORT on the child file, only parent express module has PORT listener
2. Child is using 'Router', not parent Express moudle.

Answer 4

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
    }

Answer 5

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.

Answer 6

Use:

var mymodule = require("./tools.js")

app.js:

module.exports.<your function> = function () {
    <what should the function do>
}