Process and Globals¶

The `process` Object¶

process is a global object in Node.js that provides information and control over the current Node.js process.

Access Command Line Arguments¶

console.log(process.argv);

Run:

node app.js hello world

Result:

[
  '/path/to/node',
  '/path/to/app.js',
  'hello',
  'world'
]

Use process.argv.slice(2) to ignore the first two entries.

Environment Variables¶

console.log(process.env.NODE_ENV);

Set:

NODE_ENV=development node app.js

Use .env files in real apps (with dotenv package).

Exit Code¶

process.exit(0); // success
process.exit(1); // failure

Events¶

process.on("exit", (code) => {
  console.log("Exiting with code:", code);
});

Global Variables¶

These are available in every Node.js file.

`__dirname`¶

Absolute path of the current directory.

console.log(__dirname);

`__filename`¶

Absolute path of the current file.

console.log(__filename);

`require`¶

Used to import CommonJS modules.

const fs = require("fs");

`module` and `exports`¶

Control what a module exposes.

module.exports = {}; // or exports.myFunc = ...

setTimeout and setInterval¶

Work like in the browser but run in Node’s event loop.

setTimeout(() => {
  console.log("After 1 second");
}, 1000);

const intervalId = setInterval(() => {
  console.log("Repeating");
}, 2000);

setTimeout(() => clearInterval(intervalId), 7000); // stop after 7s

Reading from stdin¶

process.stdin.on("data", (data) => {
  console.log(`You typed: ${data.toString().trim()}`);
});

To use:

node app.js
# then type something and press Enter

Summary¶

Feature	Description
`process.argv`	CLI args
`process.env`	Environment variables
`__dirname`	Current directory path
`__filename`	Current file path
`setTimeout`	Delay execution
`setInterval`	Repeat execution
`stdin/stdout`	Read/write to terminal