node-json-file-cache

A lightweight Node.js caching library that implements key-value cache storage based on local JSON files, with an API style similar to the browser's localStorage.

中文文档

⚠️ Important Notice: This is a simple single-process caching system that does not support multi-process, multi-threaded, or cluster environments. It is only suitable for command-line tools, development environments, single-machine scripts, and other single-process scenarios. For concurrent support, please use professional solutions like Redis or SQLite.

Features

• 🚀 Simple and easy to use, API design similar to localStorage
• 💾 Persistent storage based on local JSON files
• 🔑 Support for key-value pair caching
• 📁 Customizable cache file storage path
• ⚡ Lightweight with no external dependencies
• 🔒 Complete TypeScript type definitions
• 🗂️ Intelligent MD5 sharding storage, avoiding large file read/write operations
• 📊 3-level nested directory structure, optimizing file system performance

Installation

npm install node-json-file-cache

Or using yarn:

yarn add node-json-file-cache

Quick Start

JavaScript

const JsonFileCache = require('node-json-file-cache');

// Initialize cache object with cache folder path
const cache = new JsonFileCache('./cache');

// Set cache
cache.setItem('username', 'zhangsan');
cache.setItem('userInfo', { id: 1, name: 'zhangsan', age: 25 });

// Get cache
const username = cache.getItem('username');
console.log(username); // 'zhangsan'

const userInfo = cache.getItem('userInfo');
console.log(userInfo); // { id: 1, name: 'zhangsan', age: 25 }

// Remove cache
cache.removeItem('username');

// Clear all cache
cache.clear();

// Get all cache keys
const keys = cache.keys();
console.log(keys); // ['userInfo']

// Get cache item count
const length = cache.length;
console.log(length); // 1

TypeScript

import JsonFileCache from 'node-json-file-cache';

// Define type
interface UserInfo {
  id: number;
  name: string;
  age: number;
}

// Initialize cache object
const cache = new JsonFileCache('./cache');

// Set cache with type
cache.setItem<string>('username', 'zhangsan');
cache.setItem<UserInfo>('userInfo', { id: 1, name: 'zhangsan', age: 25 });

// Get cache with type hints
const username = cache.getItem<string>('username');
const userInfo = cache.getItem<UserInfo>('userInfo');

// TypeScript provides complete type checking and intelligent hints
if (userInfo) {
  console.log(userInfo.name); // Type-safe
}

API Documentation

Initialization

const cache = new JsonFileCache(cachePath, options);

Parameters:

• cachePath (string): Folder path where cache files are stored
• options (object, optional): Configuration options
  • filename (string): Cache file name, defaults to cache.json
  • autoSave (boolean): Whether to auto-save, defaults to true

Methods

setItem(key, value)

Set a cache item.

cache.setItem('key', 'value');
cache.setItem('user', { name: 'zhangsan' });

Parameters:

• key (string): Cache key name
• value (any): Cache value, supports any serializable JavaScript type

Return value: void

---

getItem(key)

Get a cache item.

const value = cache.getItem('key');

Parameters:

• key (string): Cache key name

Return value: Cache value, or null if not found

---

removeItem(key)

Delete a specific cache item.

cache.removeItem('key');

Parameters:

• key (string): Cache key name

Return value: void

---

clear()

Clear all cache.

cache.clear();

Return value: void

---

keys()

Get all cache key names.

const allKeys = cache.keys();
console.log(allKeys); // ['key1', 'key2', 'key3']

Return value: string[] - Array of all cache key names

---

length

Get the number of cache items (property).

const count = cache.length;
console.log(count); // 3

Return value: number - Number of cache items

Typical Use Cases

✅ Suitable Scenarios

1. Command-line Tool Configuration

// CLI tool saves user configuration
const cache = new JsonFileCache('~/.my-cli/cache');
cache.setItem('apiKey', 'xxx');
cache.setItem('lastUpdate', Date.now());

2. Development Environment Data Mocking

// Cache API responses during development to avoid frequent requests
const cache = new JsonFileCache('./dev-cache');
const mockData = cache.getItem('userList');
if (!mockData) {
  const data = await fetchFromAPI();
  cache.setItem('userList', data);
}

3. Single-Machine Script Data Persistence

// Web scraper script saves progress
const cache = new JsonFileCache('./crawler-cache');
cache.setItem('lastCrawledPage', 100);
cache.setItem('processedUrls', urlList);

4. Local Application Configuration Storage

// Electron app saves user preferences
const cache = new JsonFileCache(app.getPath('userData'));
cache.setItem('theme', 'dark');
cache.setItem('language', 'en-US');

❌ Unsuitable Scenarios

• Web Servers: Multi-process/cluster environments lead to data inconsistency
• High-Concurrency Applications: No locking mechanism, cannot guarantee data safety
• Distributed Systems: Does not support cross-machine cache sharing
• Scenarios Requiring Transactions: No ACID guarantees
• High Real-Time Requirements: Synchronous I/O may block the main thread

TypeScript Support

This library provides complete TypeScript type definition files (.d.ts), no need to install @types packages separately.

Type Hints

In TypeScript or JSDoc-supporting editors (like VSCode), you will get:

• Complete method parameter hints
• Return value type inference
• Detailed documentation comments
• Intelligent code completion

Generic Support

// Use generics to specify value types
const user = cache.getItem<UserInfo>('user');
const count = cache.getItem<number>('count');
const tags = cache.getItem<string[]>('tags');

Storage Architecture

This library uses an MD5 hash sharding storage strategy. For detailed design, please refer to ARCHITECTURE.md.

Core Features:

• First 3 MD5 characters serve as 3-level nested folders (e.g., a/b/c/)
• 4th MD5 character serves as file name (e.g., d.json)
• Complete MD5 used as key within files to avoid conflicts
• Theoretically supports 65,536 different file shards

Important Notes

Data Type Limitations

• Cache data is stored in JSON format, so only serializable data types are supported
• Functions, Symbols, and other non-serializable types are not supported

Concurrency Limitations

• ⚠️ Does not support multi-process concurrent access: Simultaneous read/write by multiple processes may corrupt data
• ⚠️ Does not support multi-threaded concurrent access: No file locking mechanism, thread safety not guaranteed
• ⚠️ Does not support cluster environments: Not suitable for use in Node.js cluster mode
• Recommended for use in single-process, single-threaded environments

Performance Limitations

• Suitable for small to medium-sized data caching (< 1 million records)
• File operations are synchronous, large-scale writes may impact performance
• Each read/write operation performs file I/O

Use Cases

• ✅ Local cache for single-process applications
• ✅ Temporary data storage in development environments
• ✅ Configuration cache for command-line tools
• ✅ Data persistence for single-machine scripts
• ❌ High-concurrency applications in production
• ❌ Multi-process/cluster deployed applications
• ❌ Scenarios requiring transaction support
• ❌ Browser environments

License

MIT

Contributing

Issues and Pull Requests are welcome!

Author

[Your Name]

Changelog

v1.0.0

• Initial release
• Implemented basic localStorage-style API
• Support for JSON file persistent storage