Memoise decorator

An ES7 decorator for memoising (caching) a method's response

Table of Contents

• Installation
• Compatibility
• Usage
  • Basic Usage
  • Custom Cache Key Generator
  • Memoising all method calls disregarding parameters
  • Direct access to the cache
  • Memoising arbitrary functions
• Migrating from v2

Installation

npm install @aloreljs/memoise-decorator

Compatibility

The library's only goal is to be compatible with Typescript 5 decorators which, at the time of writing, use the 2022-03 stage 3 decorators proposal. The bulk of your inputs' validation is offloaded to Typescript as well.

Usage

Basic Usage

import {Memoise} from '@aloreljs/memoise-decorator';

class MyClass {
  @Memoise()
  someMethod(a, b, c) {
  }
  
  @Memoise()
  static someStaticMethod(a, b, c) {
  }
}

Custom Cache Key Generator

The decorator uses JSON.stringify on the method arguments to generate a cache key by default, which should work for most scenarios, but can be inefficient or unusable in others. You can replace it by passing your own cache key generator to the decorator function. It will be called with the class instance as an argument.

The function can return anything that's uniquely identifiable in a Map.

import {Memoise} from '@aloreljs/memoise-decorator';

class MyClass {
  constructor() {
    this.someId = 'foo';
  }
  
  @Memoise(function(this: MyClass, label: string, data: number) {
    return `${this.someId}:${label}:${data}`;
  })
  someMethod(label: string, data: number): void {
  }
}

Memoising all method calls disregarding parameters

This might be useful for methods that don't accept parameters in the first place.

import {MemoiseAll} from '@aloreljs/memoise-decorator';

class MyClass {
  @MemoiseAll()
  method() {
    return 'foo';
  }
}

Direct access to the cache

After being called at least once, the method will get a MEMOISE_CACHE property containing the cache.

import {MEMOISE_CACHE, Memoise} from '@aloreljs/memoise-decorator';

class MyClass {
  @Memoise()
  method(a) {
    return a + 10;
  }
}
const instance = new MyClass();
instance.method(instance.method(1));
console.log(instance.method[MEMOISE_CACHE]!.get(defaultSerialiser(1))); // 11, or our argument of 1 + 10

Memoising arbitrary functions

import {memoiseArglessFunction, memoiseFunction} from '@aloreljs/memoise-decorator';

const fn1 = memoiseArglessFunction(() => Math.random());
const fn2 = memoiseFunction((a, b) => a + b);

Migrating from v2

• Instead of @Memoise.all() use @MemoiseAll()
• Typings added for MEMOISE_CACHE
• Dropped support for typescript's experimental decorators
• Added functions exports for memoising arbitrary functions