Memoize Function Utility

A robust and efficient TypeScript utility for memoizing functions with support for:

• Cache Size Limits: Control the maximum number of cached entries.
• Time-to-Live (TTL): Set expiration time for cached entries.
• LRU Cache Eviction: Automatically evict least recently used items when the cache limit is reached.
• Complex Argument Handling: Safely memoize functions with complex arguments, including objects with circular references.

Table of Contents

• Installation
• Usage
  • Basic Memoization
  • Cache Size Limit
  • Time-to-Live (TTL)
  • Handling Complex Arguments
  • Preserving this Context
  • Memoizing Asynchronous Functions
• API
  • memoize
  • MemoizeOptions
• Implementation Details
  • LRU Cache
  • Key Generation
• Testing
• License

Installation

You can install this utility via npm:

npm install @avatijs/memoize

Usage

Import the memoize function into your project:

import { memoize } from '@avatijs/memoize';

Basic Memoization

Memoize a simple function to cache its results:

function add(a: number, b: number): number {
  console.log('Computing...');
  return a + b;
}

const memoizedAdd = memoize(add);

console.log(memoizedAdd(1, 2)); // Outputs: Computing... 3
console.log(memoizedAdd(1, 2)); // Outputs: 3 (cached result)

Cache Size Limit

Limit the cache size using the maxCacheSize option:

const memoizedAddLimited = memoize(add, { maxCacheSize: 2 });

memoizedAddLimited(1, 2); // Cached
memoizedAddLimited(2, 3); // Cached
memoizedAddLimited(3, 4); // Cached, cache size exceeds limit, least recently used item is evicted

Time-to-Live (TTL)

Set a TTL (in milliseconds) after which cached entries expire:

const memoizedAddWithTTL = memoize(add, { ttl: 5000 }); // Entries expire after 5 seconds

memoizedAddWithTTL(1, 2); // Cached
setTimeout(() => {
  memoizedAddWithTTL(1, 2); // Recomputed after TTL expires
}, 6000);

Handling Complex Arguments

Memoize functions that accept complex arguments, including objects and arrays:

function processData(data: { id: number; value: string }): string {
  console.log('Processing data...');
  return `ID: ${data.id}, Value: ${data.value}`;
}

const memoizedProcessData = memoize(processData);

const data = { id: 1, value: 'Test' };
memoizedProcessData(data); // Outputs: Processing data... 'ID: 1, Value: Test'
memoizedProcessData(data); // Cached result

Preserving this Context

Memoize methods that rely on the this context:

class Multiplier {
  factor = 2;

  multiply = memoize(function (this: Multiplier, x: number) {
    return x * this.factor;
  });
}

const multiplier = new Multiplier();
console.log(multiplier.multiply(5)); // Outputs: 10

Memoizing Asynchronous Functions

Memoize functions that return promises:

async function fetchData(url: string): Promise<string> {
  const response = await fetch(url);
  return response.text();
}

const memoizedFetchData = memoize(fetchData);

memoizedFetchData('https://api.example.com/data').then(console.log);

API

memoize

Creates a memoized version of a function with optional cache size limit and TTL.

Signature

function memoize<Args extends any[], Return>(
  fn: (...args: Args) => Return,
  options?: MemoizeOptions
): (...args: Args) => Return;

Parameters

• fn: The function to memoize.
• options (optional): An object specifying memoization options.

MemoizeOptions

An interface defining the memoization options.

Properties

• maxCacheSize (optional): number
  • Maximum number of entries to store in the cache.
  • Default: Infinity
• ttl (optional): number
  • Time-to-live in milliseconds for cached entries.
  • Entries expire after ttl milliseconds.
  • Default: undefined (no expiration)

Implementation Details

LRU Cache

An internal Least Recently Used (LRU) cache is used to manage cached entries efficiently. When the cache size exceeds maxCacheSize, the least recently used item is evicted.

Key Generation

A robust key generation function handles complex arguments, including:

• Primitives: Compared by value.
• Objects: Compared by identity using a unique ID assigned via a WeakMap.
• Functions: Stringified to include their code in the key.
• Circular References: Safely handled without causing errors.

Testing

Extensive test cases have been written using Jest to ensure reliability.

Running Tests

Run the tests:

npx jest

Test Cases Covered

• Caching Basic Function Calls
• Handling Different Arguments
• Max Cache Size Limit
• Time-to-Live (TTL) Expiration
• Complex Arguments and Circular References
• Functions with Side Effects
• Preservation of this Context
• Asynchronous Functions
• Exception Handling
• Non-Serializable Arguments
• Zero TTL (No Caching)
• Multiple Memoized Functions

Changelog

Please see CHANGELOG for more information what has changed recently.

Contributing

I welcome contributions from developers of all experience levels. If you have an idea, found a bug, or want to improve something, I encourage you to get involved!

How to Contribute

1. Read Contributing Guide for details on how to get started.
2. Fork the repository and make your changes.
3. Submit a pull request, and we’ll review it as soon as possible.

License

Avati is open-source and distributed under the MIT License.