Is there a better way to structure global variables in Node.js?

Question

Is there a better way to structure global variables in Node.js?

Trying to understand what would be the best way to structure some variables. For example in my Node.js Express app, I have the following in app.js:

var poolModule = require('generic-pool');
global.pools = {
 /* ... */
};

Where pools is my global variable that keeps track of MySQL and Redis pools. I am also wondering if I can do the same with actual Redis and MySQL objects (and maybe configs variable) so I don't have to require them all over the app. And since they are going to be used the most.

Is this bad practice, and if yes, what's a better way to structure this kind of code?

Edit: added global.

node.js

Answer 1

If you require a file you are actually always requiring the same object. So that means you can do:

module.exports = {
  // same object for everybody that requires me
};

Answer 2

You have the right idea, but you want to use module.exports to export your object as a module. The CommonJS approach is to have local variables within the module and exported variables for use outside the module. In this way modules can access each others' variables through the use of require. These variables aren't really "global", but in a way are more like "friend" classes in C++. You can in fact have your poolModule do more than store variables for you--you could put methods and other functionality in there too and make it reusable across your whole application.