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limited-cacheTypeScript icon, indicating that this package has built-in type declarations

1.0.1 • Public • Published

Limited-Cache

A minimal JS cache. Like using an object to store keys and values, except it won't grow forever

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Motivation

A plain Javascript object is often good enough for simple key-value caching.

The problem is that a plain object cache can grow forever -- especially if you persist it in local storage. This library adds a size limit, plus maxCacheTime and smarter removal of old items.

Usage

The plain API provides a standard cache interface:

const recentResults = LimitedCache({
  maxCacheSize: 100,
});
recentResults.set('abc', thingToSave);
recentResults.get('abc');
recentResults.has('abc');
recentResults.getAll();
recentResults.reset();

Use LimitedCacheObject for a nicer developer experience, using Proxy:

const recentResults = LimitedCacheObject();
recentResults['abc'] = thingToSave;

Low-level functions using plain objects, if you need to stay serializable or want to store offline:

const reduxState = {
  childIdsByParentId: {},
  cacheMeta: limitedCacheUtil.init(),
};
 
// cacheMeta is a plain, serializable object that contains the cache's internal state
cacheMeta = limitedCacheUtil.set(cacheMeta, 'abc', thingToSave);
 
return {
  ...reduxState,
  childIdsByParentId: limitedCacheUtil.getAll(cacheMeta),
  cacheMeta,
};

Typescript generics, if you want to define a type for items in the cache:

const stringCache = LimitedCache<string>();
const myClassCache = LimitedCacheObject<SomeClass>();
const offlineCacheMeta = lowLevelInit<SomeObjectShape>();

Note: The React hooks were removed in v1.0 The code for useLimitedCache and useLimitedCacheObject is here if you want to implement them yourself. For most cases, a useMemo(() => LimitedCache(), [])) should be enough.

Install and Import

npm install limited-cache or yarn add limited-cache

import { LimitedCache, LimitedCacheObject, limitedCacheUtil } from 'limited-cache';

Options

maxCacheSize (number, default: 100)

Number of key/value pairs to keep in the cache. A falsy value will make it limitless.

maxCacheTime (milliseconds, default: 1 day, max: 1 year)

Time after which an item is removed. A falsy value will make it the 1-year maximum.

warnIfItemPurgedBeforeTime (milliseconds, default: 5000, development only)

If an item rotates out of the cache before this time passes, emits a warning to suggest you increase the cache size. Use a falsy value to disable.

Low-level functions

These functions are grouped together as limitedCacheUtil. The other interfaces are built on top of these.

  • init(options)
  • get(cacheMeta, cacheKey)
  • getAll(cacheMeta) - returns the entire cache, excluding expired items
  • has(cacheMeta, cacheKey)
  • set(cacheMeta, cacheKey, value)
  • remove(cacheMeta, cacheKey)
  • reset(cacheMeta)
  • setOptions(cacheMeta, options) - you can update options anytime

You can also import these functions individually, if you want to optimize tree-shaking and minification:

import { lowLevelInit, lowLevelGetOne, lowLevelGetAll, lowLevelSet } from 'limited-cache';

FAQ

Immutable?

The cache itself is, but the low-level cacheMeta is persistent/mutated.

API for bulk operations?

Only reset and getAll. The other actions aren't as optimizable, so they're omitted to keep this small.

When are old items removed?

When new items are added, or if you try to get an item that has expired.

Is this a least-recently-used cache?

No: For performance it only tracks by set time.

If you want items to expire based on when they were last accessed (instead of when they were set), you can set the value that already exists: only the timestamp will be updated, so performance won't suffer.

Install

npm i limited-cache

DownloadsWeekly Downloads

59

Version

1.0.1

License

MIT

Unpacked Size

159 kB

Total Files

29

Last publish

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