Node.js is a Javascript engine (Google’s V8 engine for Chrome, written in C++) that allows to run Javascript outside the browser. While numerous libraries are available for extending Node’s functionalities, the engine comes with a set of core modules implementing basic functionalities.
There’s currently 34 core modules included in Node:
[ 'assert',
'buffer',
'c/c++_addons',
'child_process',
'cluster',
'console',
'crypto',
'deprecated_apis',
'dns',
'domain',
'Events',
'fs',
'http',
'https',
'module',
'net',
'os',
'path',
'punycode',
'querystring',
'readline',
'repl',
'stream',
'string_decoder',
'timers',
'tls_(ssl)',
'tracing',
'tty',
'dgram',
'url',
'util',
'v8',
'vm',
'zlib' ]
This list was obtained from the Node documentation API https://nodejs.org/api/all.html (JSON file: https://nodejs.org/api/all.json).
assert The assert module provides a simple set of assertion tests that can be used to test invariants.
buffer Prior to the introduction of TypedArray in ECMAScript 2015 (ES6), the JavaScript language had no mechanism for reading or manipulating streams of binary data. The Buffer class was introduced as part of the Node.js API to make it possible to interact with octet streams in the context of things like TCP streams and file system operations.
Now that [TypedArray](<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray>) has been added in ES6, the Buffer class implements the [Uin t8Array](<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array>) API in a manner that is more optimized and suitable for Node.js' use cases.
c/c++_addons Node.js Addons are dynamically-linked shared objects, written in C or C++, that can be loaded into Node.js using the require() function , and used just as if they were an ordinary Node.js module. They are used primarily to provide an interface between JavaScript running in Node.js and C/C++ libraries.
child_process The child_process module provides the ability to spawn child processes in a manner that is similar, but not identical, to popen(3).
cluster A single instance of Node.js runs in a single thread. To take advantage of multi-core systems the user will sometimes want to launch a cluster of Node.js processes to handle the load. The cluster module allows you to easily create child processes that all share server ports.
console The console module provides a simple debugging console that is similar to the JavaScript console mechanism provided by web browsers.
crypto The crypto module provides cryptographic functionality that includes a set of wrappers for OpenSSL's hash, HMAC, cipher, decipher, sign and verify functions.
deprecated_apis Node.js may deprecate APIs when either: (a) use of the API is considered to be unsafe, (b) an improved alternative API has been made available, or (c) breaking changes to the API are expected in a future major release.
dns The dns module contains functions belonging to two different categories:
domain This module is pending deprecation. Once a replacement API has been finalized, this module will be fully deprecated. Most end users should not have cause to use this module. Users who absolutely must have the functionality that domains provide may rely on it for the time being but should expect to have to migrate to a different solution in the future.
Events Much of the Node.js core API is built around an idiomatic asynchronous event-driven architecture in which certain kinds of objects (called “emitters”) periodically emit named events that cause Function objects (“listeners”) to be called.
fs File I/O is provided by simple wrappers around standard POSIX functions. To use this module do require('fs'). All the methods have asynchronous and synchronous forms.