Node.js global variables

Making use of global variables

Despite the cautionary note, there are situations where globals come in handy. For example, if you've got a library like underscore.js and you want it accessible across your app:

global._ = require('underscore'); // POOF! Underscore.js is now accessible globally!
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Just remember to always namespace your global variables, preventing possible clashes:

global.MYAPI = {}; // MYAPI is your new playground. Don't worry - it's global!
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Controlled usage of global variables

Always remember, global variables are like a toilet in an open office, very convenient but can cause trouble if not handled properly. Use them judiciously:

// globals.js
module.exports = {
  sharedConfig: 'Config Value', // Functioning like the office jukebox playing your favorite song
};

// In another module
const globals = require('./globals.js');
console.log(globals.sharedConfig); // Prints 'Config Value' to the console
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Beyond Global Variables

If you constantly find yourself reaching for globals, it may be a sign that your code needs refactoring or better organization. A possible solution to keep your code manageable and sane is dependency injection:

// Make sure to keep your friends(close modules) closer
const db = require('./db');

function serviceA(dbInstance) {
  // Operate using dbInstance
  // "Hello, dependency injection here for you!"
}

serviceA(db);
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Use with caution: this in node.js

In Node.js, this can be a tricky proposition - don't assume it's the global object:

console.log(this === global); // This will log: false. Plot twist, isn't it! 
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The config.js way

If you’re dealing with configurations or settings, a neat way of dealing with this is to create a single config.js (or similarly named) file that exports an object with all your configurations:

// config.js
module.exports = {
  appName: 'SharedApp',
  version: '1.0.0',
};

// In any other module
const config = require('./config');
console.log(config.appName);  // SharedApp - Isn't JS lovely?
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