Core APIs

What are Node’s Core APIs?

Node.js ships with a rich set of built-in globals and modules that are available without installing anything. These are the primitives every Node.js program is built on.

Key globals and modules covered in this module:

process — access to the running process: environment variables, command-line arguments, the working directory, the platform, and lifecycle control.
Buffer — a fixed-length chunk of raw binary data. Predates typed arrays and remains the standard way to work with bytes in Node streams and networking.
node:fs / node:fs/promises — read, write, and navigate the filesystem. The promises API lets you use async/await natively.
EventEmitter — the backbone of Node’s event-driven architecture. Streams, the HTTP server, and many third-party libraries all extend EventEmitter.

What this module covers

Lesson	Topic
process & env	`process.argv`, `process.env`, exit codes, and platform detection
Buffer	Binary data, encodings, and byte-level manipulation
File System	`fs` callbacks, sync APIs, and the `fs/promises` interface
EventEmitter	Custom events, listeners, and the `once` / `removeListener` lifecycle

A first globals demo

The snippet below reads two globals that are available in every Node.js process without any require or import:

Node.js

// process.version — the running Node.js version
console.log('Node version: ' + process.version);

// Buffer.byteLength — bytes used to store a string (UTF-8 by default)
var str = 'Hello, Node!';
console.log('String: ' + str);
console.log('Chars: ' + str.length);
console.log('Bytes (UTF-8): ' + Buffer.byteLength(str, 'utf8'));

Needs the Node.js runtime — open in StackBlitz to run.

Which of the following is a true Node.js global — available without any import? fs path process http

What is the recommended modern prefix for importing a Node.js built-in module? No prefix — just "fs" The "node:" prefix — e.g. "node:fs" The "@node/" scope — e.g. "@node/fs" Built-ins cannot be imported with ESM