Global variable not working in NodeJS

Question

I am trying to get global variables working in node.js, but it seems like I don't really understand the concept, even though my understanding matches the documentation.

Minimal example

My main.js file, which is compiled using rollup is:

global.a = 1;
require('./core/test.js');

My core/test.js file is simply:

console.log(a);

This causes the error:

Uncaught ReferenceError: a is not defined

The fully compiled output is:

(function (exports) {
'use strict';

var commonjsGlobal = typeof window !== 'undefined' ? window : typeof global !== 'undefined' ? global : typeof self !== 'undefined' ? self : {};

console.log(a);

commonjsGlobal.a = 1;

}((this.LaravelElixirBundle = this.LaravelElixirBundle || {})));
//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjpudWxsLCJzb3VyY2VzIjpbIkM6L3dhbXAvd3d3L3V1YmMvcmVzb3VyY2VzL2Fzc2V0cy9qcy9jb3JlL3Rlc3QuanMiLCJDOi93YW1wL3d3dy91dWJjL3Jlc291cmNlcy9hc3NldHMvanMvYXBwLmpzIl0sInNvdXJjZXNDb250ZW50IjpbImNvbnNvbGUubG9nKGEpO1xyXG4iLCJnbG9iYWwuYSA9IDE7XHJcbnJlcXVpcmUoJy4vY29yZS90ZXN0LmpzJyk7XHJcbiJdLCJuYW1lcyI6WyJnbG9iYWwiXSwibWFwcGluZ3MiOiI7Ozs7O0FBQUEsT0FBTyxDQUFDLEdBQUcsQ0FBQyxDQUFDLENBQUMsQ0FBQzs7QUNBZkEsY0FBTSxDQUFDLENBQUMsR0FBRyxDQUFDLENBQUM7OyJ9

It seems that a gets defined after console.log(a);. I'm not 100% sure if this matters in JS but it could be causing the error.

So my question is: what causes this, and what am I doing wrong here?

Possibly relevant information: I'm using Laravel Elixir to compile everything.

Note: Please don't post discussion on whether or not to use global variables in node.js or in general. I know it's usually a bad idea, but I have a very good reason to do it in this case.

Edit: Additional context

What I'm really trying to do is getting Zurb Foundation to work with Laravel Elixir though node.js. I installed foundation-sites through NPM. foundation-sites relies on jquery, which it pulls in itself. However, Foundation doesn't seem to follow the usual conventions of just using something like var jquery = require('jquery'); in its own js file. It actually relies upon a global jQuery variable being available. Therefore I have to ensure that somehow.

My actual file looks like this:

global.jQuery = global.$ = require('jquery');
require('foundation-sites');

So if there are any Foundation/Laravel-specific anwers I would be very happy to hear them as well. Is there something I'm not getting, or did Foundation just not create their package the "right" way?

Answer 1

It looks to me like an issue with your bundler not respecting the order you're doing those two lines in. Your source is clearly:

global.a = 1;
require('./core/test.js');

...but the bundled result is clearly the other way around:

console.log(a);
commonjsGlobal.a = 1;

It seems like it's hoisting the require calls. In general, having require calls that need to be done at a particular point in the execution control flow is not best practice (in fact, when defining modules for ES2015, import is explicitly defined as not being executed in the module's step-by-step control flow).

So if you need to do this, you'll probably want to look at another bundler. But check that it supports order other than dependency resolution order.

Answer 2

You are right that it should work. Here's a working example:

// file1.js
global.a = 'hello';
require('./file2');

// file2.js
console.log(a);

Run node file1.js, and you'll see 'hello' printed to the console.

It looks like you've got some other tool being used (Laravel / Elixir). Use node directly and see what happens.

Answer 3

Alright I solved this in a pretty simple way, by using browserify instead of rollup. Thanks for the other answers pointing me in the right direction. It's not a perfect solution, and I still don't fully understand what the differences are between the two, but it'll do for this project.

The relevant part of my gulpfile:

mix.browserify('app.js','public/js/app.js');

To use browserify with Laravel Elixir, I used

npm install laravel-elixir-browserify-official --save-dev

Answer 4

I solved this for rollup by providing an output.intro that sets up the required variables. In your case this would be:

// rollup.config.js
export default {
  // ...
  output: {
    // ...
    intro: `let a = 1;`
  }
};

Admittedly this qualifies as a hack, but solves the bundling problem in my case (where switching away from rollup is not an option).

Answer 5

Same problem, only when using import. Solved the problem this way:

// main.js
import './globals.js';
import './file.js';

// globals.js
global.a = 123;

// file.js
console.log(a);