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Node.js Core Modules

Essential Node.js built-in modules including File System, HTTP, Process, OS, Crypto, Streams, and Events

15 min read
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Official Docs

File System (fs)

Read, write, and manipulate files and directories

File Operations

Read, write, delete files with async and sync methods

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🟢 Essential - Every Node.js app deals with files
💡 Use async methods (fs.promises) to avoid blocking
⚠️ Always handle errors in file operations
📌 Use path.join() for cross-platform paths
⚡ Stream large files instead of reading all at once
🔗 Related: fs-extra for additional utilities

Path Module

Work with file and directory paths across platforms

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🟢 Essential - Handle paths correctly on all OS
💡 Always use path.join() not string concatenation
📌 __dirname is current file's directory
⚡ path.resolve() creates absolute paths
⚠️ Windows uses \ while Unix uses /
🔗 Related: process.cwd() for working directory

Directory Operations

Create, read, and remove directories

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💡 Use recursive: true to create nested directories
⚡ readdir with withFileTypes avoids extra stat calls
⚠️ fs.rm() with force: true is like rm -rf (dangerous)
📌 Watch has platform-specific limitations
🔗 Related: glob for pattern matching
filesystemdirectories

HTTP & HTTPS

Create servers and make HTTP requests

HTTP Server

Create HTTP servers to handle web requests

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🟢 Essential - Foundation of web servers in Node.js
💡 Use Express.js for production applications
📌 Server emits events: request, connection, close
⚡ Use cluster module for multi-core utilization
⚠️ Handle server errors to prevent crashes
🔗 Related: https module for SSL/TLS

HTTP Client Requests

Make HTTP requests to external APIs and services

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💡 Consider using axios or node-fetch for easier API
📌 Response is a readable stream
⚡ Set timeout to prevent hanging requests
⚠️ Always handle network errors
🟢 Essential for API integration
🔗 Related: https.request() for secure requests

Process & OS

Interact with system processes and operating system

Process Module

Access command line arguments, environment, and control process

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🟢 Essential - Control Node.js runtime behavior
💡 process.env for environment variables
📌 process.argv contains command line arguments
⚠️ process.exit() immediately terminates (use carefully)
⚡ process.nextTick() for async scheduling
🔗 Related: dotenv for .env file loading

OS Module

Get operating system information and utilities

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💡 Useful for system monitoring and diagnostics
📌 os.platform() returns darwin, win32, linux
⚡ os.cpus() for CPU info and core count
🟢 Essential for cross-platform apps
🔗 Related: systeminformation for detailed stats

Child Process

Execute system commands and spawn new processes

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💡 exec for simple commands, spawn for complex/streaming
⚠️ Sanitize user input to prevent command injection
📌 fork() is specifically for Node.js scripts
⚡ Use worker_threads for CPU-intensive tasks instead
🔗 Related: execa for better child process handling
processsystem

Crypto & Buffer

Cryptography operations and binary data handling

Crypto Module

Cryptographic functionality for hashing, encryption, and security

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🟢 Essential - Security and data integrity
💡 Use crypto.randomBytes() for secure random values
⚠️ Never use Math.random() for security
📌 bcrypt is better for password hashing
⚡ Use streaming API for large files
🔗 Related: jsonwebtoken for JWT tokens

Buffer Module

Handle binary data and convert between encodings

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💡 Buffers are fixed-size byte arrays
📌 Use Buffer.from() not new Buffer() (deprecated)
⚡ Buffers are more memory efficient than strings
⚠️ Be careful with buffer overflows
🔗 Related: stream.Buffer for streaming operations

Streams & Events

Handle streaming data and event-driven programming

Streams

Process data piece by piece without loading all into memory

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🟢 Essential - Handle large files and real-time data
💡 Four types: Readable, Writable, Duplex, Transform
⚡ Streams save memory and improve performance
📌 pipe() handles backpressure automatically
⚠️ Always handle stream errors
🔗 Related: stream/promises for async iteration

Event Emitter

Create and handle custom events for async communication

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🟢 Essential - Core of Node.js event-driven architecture
💡 Many Node.js objects extend EventEmitter
📌 removeListener() to prevent memory leaks
⚠️ Default max 10 listeners (setMaxListeners to change)
⚡ once() for one-time event handlers
🔗 Related: events.EventEmitter is the base class

Utilities & Advanced

Utility functions and advanced Node.js features

URL & QueryString

Parse and construct URLs and query strings

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🟢 Essential - URL parsing for web applications
💡 Use new URL() instead of legacy url.parse()
📌 URLSearchParams for easy query manipulation
⚡ URL validation happens in constructor
🔗 Related: path module for file paths
urlutilities

Util Module

Utility functions for debugging and promisification

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💡 promisify() converts callbacks to promises
📌 util.inspect() is great for debugging
⚡ TextEncoder/Decoder for UTF-8 conversion
🟢 Essential for modernizing callback code
🔗 Related: console.dir() for simple inspection
utilitiesdebugging

Worker Threads

Run JavaScript in parallel threads for CPU-intensive tasks

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🔴 Advanced - For CPU-intensive parallel processing
💡 Workers run in separate V8 isolates
⚠️ No shared memory (use SharedArrayBuffer carefully)
⚡ Better than child_process for JavaScript code
📌 Not for I/O operations (use async/await instead)
🔗 Related: cluster for network server scaling
parallelperformance

Cluster Module

Scale Node.js apps across multiple CPU cores

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🟢 Essential for production Node.js servers
💡 Workers share server ports automatically
⚡ Scales to all CPU cores for better performance
📌 Master process manages workers
⚠️ Workers die independently, implement restart logic
🔗 Related: pm2 for production process management
scalingperformance

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