cached-observable

cached-observable

A simple utility to cache RxJS Observables in memory, Session and Local Storage

This utility allows you to cache streams in memory, or Web Storage. It also works in Node, but please only use in-memory if you do so.

In the future, it will be extended with he ability provide a way to provide a custom CacheProviderType, such as Redis.

Install

npm i cached-observable --save

Usage

Interface

The utility has the following interface:

function cachedObservable<T = unknown>(
    observable$: Observable<T>,
    key: string,
    maxAge?: number | undefined,
    cacheProviderType = CacheProviderType.Memory,
)

• observable$ is the stream we want to cache
• key is a unique key - please make sure it is unique
• maxAge is a value, in milliseconds, that represents the amount of time the value will be cached for
• cacheProviderType is by default in-memory, you can also choose CacheProviderType.Persistent or CacheProviderType.Session

Basic Example

A basic example; the stream is cached in memory for the whole duration of the session.

import { cachedObservable } from 'cached-observable';

function getTodos() {
  const request$ = this.http.get(url);
  const key = url;
  
  return cachedObservable(request$, key);
}

Expiry Time

We can set a max-age - so that the entry will expire after the number of milliseconds provided

import { cachedObservable } from 'cached-observable';

function getTodos() {
  const request$ = this.http.get(url);
  const key = url;
  const maxAge = 60_000; // 1 minute
  
  return cachedObservable(request$, key, maxAge);
}

Web Storage

We can store the streams in both session and local storage:

import { cachedObservable, CacheProviderType } from 'cached-observable';

// local storage
function getTodos() {
  const request$ = this.http.get(url);
  
  return cachedObservable(request$, url, maxAge, CacheProviderType.Persistent);
}

// session storage
function getTodos() {
  const request$ = this.http.get(url);

  return cachedObservable(request$, url, maxAge, CacheProviderType.Session);
}

Invalidating Cache

import { invalidateCachedObservable } from 'cached-observable';

invalidateCachedObservable(cacheKey, CacheProviderType.Session);