Matt at Keyboard Writes Code

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Esqlate Cache

October 15, 2019 — Matt Forrester
Why does this exist?

Esqlate Cache is a really basic in-memory cache which has a few interesting properties:

  • You initialize the cache with the function to retrieve the value from the original source, enabling you to write cache(params) everywhere, whether the item is cached or not. The reason for this is that I found that anything which I wanted to cache was nearly always something that was IO based that I wanted to dependency inject anyway and I would always DI both the cache and the IO operation. Would it not be better to dependency inject one thing?
  • It handles race conditions nicely. If a result for a set of parameters is already in the process of being acquired, it will not not start acquiring another, but will return the one result to both requesters.
  • It realistically only caches the result from one (promise based) function. I think this is a good thing because it helps TypeScript typing and thus, greatly helps readability.
How do you use it?

Usage is quite simple:

import getCache, { EsqlateCache } from "esqlate-cache";

// Parameters can be whatever you like, and however many you wish, but they must be JSON serializable.
function getStatusCodeForUrl(p: string): Promise<number> {
    fetch(url).then((resp) => resp.status);

const cache: EsqlateCache<number> = getCache(getStatusCodeForUrl);

const uncachedResult = await cache("");
const cachedResult = await cache("");
const anotherUncachedResult = await cache("");
How do I install it?

The code is clone-able from here but it you would normally npm install esqlate-cache.

What is the license?

It's MIT licensed.

You can find this project at GitHub. Tags: typescript, javascript, caching, io, types, race-condition, library