How to realy include a js file in Node.js

Question

I did't found any realy working solution of this issue on Google, so...

There is a module called vm, but people say it is very heavy. I need some simple function, like PHP's include, which works like the code of an including file inserts right into the place in code you need and then executes.

I tryed to create such function

function include(path) {
    eval( fs.readFileSync(path) + "" );
}

but it is not as simple... it is better if I'll show you why in example.

Let's say I need to include file.js file with content

var a = 1;

The relative file look like this

include("file.js");
console.log(a); // undefined

As you already realized a is undefined because it is not inherits from a function.

Seems the only way to do that is to type this long creepy code

eval( fs.readFileSync("file.js") + "" );
console.log(a); // 1

every time with no wrapper function in order to get all the functionality from a file as it is.

Using require with module.exports for each file is also a bad idea...

Any other solutions?

Why is using require a bad idea? Isn't that basically what everybody else in the Node world uses? — Pointy
– Pointy, Commented Jan 26, 2014 at 17:24
because with require I have to append each my variable to module.exports object — artnikpro
– artnikpro, Commented Jan 26, 2014 at 17:26
@artnikpro: Which is a good thing. It makes you think in terms of keeping variables close to your chest, only exposing those you have to. :-) — T.J. Crowder
– T.J. Crowder, Commented Jan 26, 2014 at 17:44

T.J. Crowder · Accepted Answer · 2014-01-26 17:44:19Z

7

Using require with module.exports for each file is also a bad idea...

No, require is the way you do this in NodeJS:

var stuff = require("stuff");
// Or
var stuff = require("./stuff"); // If it's within the same directory, part of a package

Break your big vm into small, maintainable pieces, and if they need to be gathered together into one big thing rather than being used directly, have a vm.js that does that.

So for example

stuff.js:

exports.nifty = nifty;
function nifty() {
    console.log("I do nifty stuff");
}

morestuff.js:

// This is to address your variables question
exports.unavoidable = "I'm something that absolutely has to be exposed outside the module.";

exports.spiffy = spiffy;
function spiffy() {
    console.log("I do spiffy stuff");
}

vm.js:

var stuff     = require("./stuff"),
    morestuff = require("./morestuff");

exports.cool = cool;
function cool() {
    console.log("I do cool stuff, using the nifty function and the spiffy function");
    stuff.nifty();
    morestuff.spiffy();
    console.log("I also use this from morestuff: " + morestuff.unavoidable);
}

app.js (the app using vm):

var vm = require("./vm");

vm.cool();

Output:

I do cool stuff, using the nifty function and the spiffy function
I do nifty stuff
I do spiffy stuff
I also use this from morestuff: I'm something that absolutely has to be exposed outside the module.

edited Jan 26, 2014 at 17:44

answered Jan 26, 2014 at 17:25

T.J. Crowder

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5 Comments

Karolis Over a year ago

replace 'stuff.js' with 'stuff' to set a better example?

artnikpro Over a year ago

so how do I get a variable this way? Do I have to append it to module.exports object (and each other variable in the file)?

T.J. Crowder Over a year ago

@artnikpro: Variables should be contained (restricted) as much as possible. So each bit (stuff, in the above) would have variables it used to provide the functionality it exposes. If you need to make a variable available outside of stuff, yes, put it on exports, and use it directly from there inside stuff (so you aren't getting out of sync). But again, best to keep things contained whenever possible.

artnikpro Over a year ago

Well, it is pretty strange way for me. I am new in node.js, usually developed in PHP and client-side JS, so I think I will need some time to use to it. Thanks!

T.J. Crowder Over a year ago

@artnikpro: You're welcome! It's not so much a NodeJS thing, it's a modularity thing -- which NodeJS actively encourages. :-)

Maroshii · Accepted Answer · 2014-01-26 18:03:28Z

What you are trying to do breaks modularity and goes against Node.js best practices.

Lets say you have this module (sync-read.js):

var fs = require('fs');

module.exports = {
  a: fs.readFileSync('./a.json'),
  b: fs.readFileSync('./b.json'),
  c: fs.readFileSync('./c.json')
}

When you call the module the first time ...

var data = require('./sync-read');

... it will be cached and you wont read those files from disk again. With your approach you'll be reading from disk on every include call. No bueno.

You don't need to append each of your vars to module.exports (as in comment above):

var constants = {
  lebowski: 'Jeff Bridges',
  neo: 'Keanu Reeves',
  bourne: 'Matt Damon'
};

function theDude() { return constants.lebowski; };
function theOne() { return constants.neo; };
function theOnly() { return constants.bourne; };

module.exports = {
  names: constants,
  theDude : theDude,
  theOne : theOne
  // bourne is not exposed
}

Then:

var characters = require('./characters');

console.log(characters.names);

characters.theDude();
characters.theOne();

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