instance-memoize

flexible cache wrapper for js object.

Getting Started

Prerequisites

• Node.js v8+
• npm or yarn

Installing

$ npm add instance-memoize

Usage

basic example

instance-memoize cached results of method invocation on the specified object permanently. If you want to manage cache purging and lifetime see [custom cache example](#with custom cache).

import memoize from 'instance-memoize'; // or const memoize = require('instance-memoize') for commonjs modules

const obj = {
  calledCounter: 0,
  method: function() {
    calledCounter++;
    return "test value";
  }
};

const wrapped = memoize({
  instance: obj,
  methods: ['method']
})

console.log(wrapped.method())      // output => "test value"
console.log(wrapped.calledCounter) // output => "1"

/*
  The result of "method" is stored internal cache,
  From the second call, the result is returned via cache.
 */
console.log(wrapped.method())      // output(from cache) => "test value"  
console.log(wrapped.calledCounter) // output => "1"

with es2015 classes

import memoize from 'instance-memoize'; // or const memoize = require('instance-memoize') for commonjs modules

class Sample {
  constructor() {
    this.calledCounter = 0;
  }
  someMethod() {
    this.calledCounter++;
    return "value";
  }
}

const wrapped = memoize({
  instance: new Sample(),
  methods: ['someMethod']
})

console.log(wrapped.someMethod())      // output => "test value"
console.log(wrapped.calledCounter)     // output => "1"

console.log(wrapped.someMethod())      // output(from cache) => "test value"  
console.log(wrapped.calledCounter)     // output => "1"

with async functions

instance-memoize also works with async/await or Promise.

import memoize from 'instance-memoize'; // or const memoize = require('instance-memoize') for commonjs modules

class Sample {
  constructor() {
    this.calledCounter = 0;
  }
  async someMethod() {
    this.calledCounter++;
    return "value";
  }
}

const wrapped = memoize({
  instance: new Sample(),
  methods: ['someMethod']
})

console.log(await wrapped.someMethod())   // output => "test value"
console.log(wrapped.calledCounter)        // output => "1"

console.log(await wrapped.someMethod())   // output(from cache) => "test value"  
console.log(wrapped.calledCounter)        // output => "1"

with custom cache

You can use your customized cache by passing cache instance via options. cache instance must implement three methods;

• get(key: string) :Object
• set(key: string, obj: any)
• reset()

This example shows instance-memoize working with isaacs's node-lru-cache.

import memoize from 'instance-memoize'; // or const memoize = require('instance-memoize') for commonjs modules
import LRU from 'lru-cache' // import isaacs's node-lru-cache

class Sample {
  constructor() {
    this.calledCounter = 0;
  }
  someMethod() {
    this.calledCounter++;
    return "value";
  }
}

const wrapped = memoize({
  instance: new Sample(),
  methods: ['someMethod'],
  options: {
    cache: LRU({ ...lruCacheOptions })
  }
})

API

memoize(instance, [...methodNames], options)

arguments

• instance (Object): Source object that wrapped to.
• methodNames (Array): Method name(s) that cached.
• options (Object):
  • cache (Object): Custom Cache object
  • keygen (function(methodName: string, ...args): string ): cache key generator function

returns

(Object): Wrapped instance that caches the result of specified method invocation.

Authors

• Akito Ito - Initial work - akito0107

License

This project is licensed under the Apache2.0 License - see the LICENSE.md file for details