Quartz 4

Global objects

2 min read

These global objects are core to working with Node.js. Let’s break them down one by one.

🌍 1. global

  • Equivalent to window in the browser.

  • It’s the global namespace object in Node.js.

  • Variables or functions attached to global can be accessed anywhere in your app.

Example:

global.myVar = 123;
 
console.log(myVar); // 123

⚠️ Best practice: Avoid polluting global — it makes code harder to debug and maintain. Instead, use modules.

⚙️ 2. process

  • A built-in object that gives info and control over the current Node.js process.

  • Always available — no require needed. See Require

Common uses:

console.log(process.pid); // Process ID
console.log(process.cwd()); // Current working directory
console.log(process.env.NODE_ENV); // Environment variables
 
process.on("exit", () => {
  console.log("Process is exiting");
});

Key things:

  • process.argv → command-line arguments (node app.js arg1 arg2)

  • process.env → environment variables (used for configs/secrets)

  • process.exit() → force quit the app

📂 3. __dirname

  • Returns the absolute path of the directory containing the currently executing file.

Example:
If your file is at /Users/tyson/project/app.js:

console.log(__dirname);
// /Users/tyson/project

Useful when working with file paths (fs, path).

📄 4. __filename

  • Returns the absolute path of the current file (including the file name).

Example:

console.log(__filename);
// /Users/tyson/project/app.js

📝 Key Difference: process.cwd() vs __dirname

  • process.cwd() → current working directory where Node was started.

  • __dirname → directory of the script file itself.

Example:

cd /Users/tyson
node project/app.js

Inside app.js:

  • process.cwd() → /Users/tyson

  • __dirname → /Users/tyson/project

✅ In short:

  • global → global scope object (avoid using).

  • process → info/control of Node process (env vars, args, lifecycle).

  • __dirname → folder path of current file.

  • __filename → full file path of current file.

Do you want me to show you practical use cases (like how __dirname + path.join are used when serving static files), or should we move on to the next Node core concept (e.g., Modules & require)?

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