Installation

yarn add latermom --save

Usage

const { Cache } = require("latermom")

const maxSize = 2 // will limit max cache size upon cache.get()
const getUser = async (id) => {
  const response = await fetch("https://dummyjson.com/users/" + id)
  const { firstName, lastName, address } = await response.json()

  return {
    id,
    name: `${firstName} ${lastName}`,
    address,
  }
}

const usersCached = new Cache(getUser, maxSize)

Promise.all([
  usersCached.get(1),
  usersCached.get(2),
  usersCached.get(3),
  usersCached.get(4),
]).then((users) => {
  console.log(usersCached.data) // contains only last maxSize users (3 and 4)
  console.log(usersCached.size) // 2
})

const { Cache } = require("latermom")
// create cache with factory function (may take any number of parameters)
const cache = new Cache(() => Math.random())

// each time you call the cache.get with same parameters
// you will get the same once lazy cached answer
const a = cache.get(1, 2, 3)
const b = cache.get(1, 2, 3) // this will return the same as above
const c = cache.get(1, 2)
const d = cache.get(1, 2, 4)

console.log(a === b) // true
console.log(a !== c) // true
console.log(a !== d) // true

API

class Cache<T = unknown> {
  constructor(factoryFunction: (...args: any[]) => T, maxSize: number = Infinity) {
    //
  }
}

• creates a LaterMom (Lazy Map) instance with factory function for lazy cache

methods

• get(...args: any[]): T - get entry at key created from args, lazy instantiated by factory
• createKey(...args: any[]): string - creates string key
• create(...args: any[]): T - wrapped factory function
• hasKey(key: string): boolean - check if has entry at key
• has(...args: any[]): boolean - check if has entry at key created from args
• deleteKey(key: string): boolean - deletes entry from data at key
• delete(...args): boolean - deletes entry from data at key created from args
• size: number - returns size of data
• maxSize: number - on insert the oldest items are deleted until reached maxSize

properties:

• data: Map

Tests

$ jest
 PASS  ./index.test.js
  ✓ Calls factory once when asked for same key many times (62 ms)
  ✓ Getter is able to handle multiple arguments
  ✓ Readme has working code (1 ms)

Test Suites: 1 passed, 1 total
Tests:       3 passed, 3 total
Snapshots:   0 total
Time:        0.946 s, estimated 1 s
Ran all test suites.
Done in 1.44s.

License

MIT

Author

Jacek Pietal @ 2019-2021