Custom cache object to be used with Re-reselect. It utilizes a Weak Map so that both the cache key object and selectorFn can be garbage collected.

import createCachedSelector from 're-reselect';
import { FlatWeakMapCache } from 're-reselect-flat-weak-map-cache';

createCachedSelector()({
  // ...
  keySelector,
  cacheObject: new FlatWeakMapCache()
});

See example for full usage.

By default, only allows string or number cache keys. It does provide a few custom cache objects that will allow any type as a cache key. These objects, like FlatMapCache, utilize a Map.

The downside with using a Map is that any object you use as a key and its associated selectorFn will not be garbage collected. Even if the object used as a key is no longer referenced in the application.

While this likely won't be an issue for most applications, the associated memory leaks could be a problem for memory intensive applications.

I've provided an example to illustrate a use case you've probably seen in Redux applications.

To follow best practices, objects are treated as immutable: any change to an object should yield a new object, not mutate the original. If that object is used as a cache key, each iteration of the object will not be able to be garbage collected. And each selectorFn associated with that key will not be garbage collected.

Conversely, a weak map holds a weak reference to the key object. So if there are no other references to the object, it and its value will be garbage collected.

• patrick-steele-idem - identified the problem with memory leaks using caching selectors

• Publish to NPM
• Add another cache object that will handle a key that can be a primitive type as well (weak maps don't allow primitive types)
• This is my first NPM package, and I may not have followed best practices, so I plan to follow this tutorial to improve this package structure
• More descriptive errors when attempting to use a primitive type as a key

• Re-reselect
• Re-reselect: Write Your Custom Cache Object