@typescript-first/simple-cache v0.1.1

TypeScript First: Simple Cache Wrapper

Allow an async function' calls to be cached and have its cached invalidated in an unopinionated, declarative manner. The intention is to save repeated reads over network partitions such as sending GET requests on the client side or querying database reads from the server side.

Installation

npm install @typescript-first/simple-cache

Usage

Suppse we have a function expensiveUpperCase. Upper-casing isn't really expensive, we'll artifically make it so.

async function expensiveUpperCase(input: string) {
  await new Promise(resolve => setTimeout(resolve, 5000));
  return input.toUpperCase();
}

We can produce the cached version of the function like this:

import { withCache } from "@typescript-first/simple-cache";
const cachedExpensiveUpperCase = withCache(expensiveUpperCase, {
  paramHasher: (input: string) => string,
  paramState: (input: string) => null,
  maxEntries: 10
});

In general:

withCache(inputFunction, cacheSettings);

In the cacheSettings object:

• You provide a paramHasher to produce a string that is used to look up a cache entry based on your function's input argument value. So this should be unique for each possible argument value.
• You provide a paramState to associate a state to a cache entry. When the state changes on a subsequent call, the previous cached value is invalidated. In the example above, our computation is stateless so we just statically return a constant null -- the constant outcome means that the cache will be perpetually valid.
• You provide how many cache entries to retain. Cache entries least recently used will be kicked out once the limit is exceeded.

The cached version of the function has exactly the same signature as the input function.

cacheExpensiveUpperCace("hello");

Current limitations

The input function must be async and must accept only one parameter.