JS-EasyCache

This is a easy & fast library that emulates memcache functions using HTML5 localStorage with lossless data compression support, so that you can cache data on the client and associate an expiration time with each piece of data. If the localStorage limit (~5MB) is exceeded, it tries to create space by removing the items that are closest to expiring anyway. If localStorage is not available at all in the browser, the library degrades by simply not caching and all cache requests return null.

JS-EasyCache uses high-performance lossless data compression algorithm to make data stored size smaller so you can store more data to the localStorage.

Methods

The library exposes 9 methods: set(), get(), remove(), flush(), flushExpired(), setBucket(), resetBucket(), supported(), and enableWarnings().

EasyCache.set

Stores the value in localStorage. Expires after specified number of minutes.

Arguments

1. key (string)
2. value (Object|string)
3. time (number: optional)

EasyCache.get

Retrieves specified value from localStorage, if not expired.

Arguments

1. key (string)

Returns

string | Object : The stored value. If no value is available, null is returned.

EasyCache.remove

Removes a value from localStorage.

Arguments

1. key (string)

EasyCache.flush

Removes all EasyCache items from localStorage without affecting other data.

EasyCache.setBucket

Appends CACHE_PREFIX so EasyCache will partition data in to different buckets

Arguments

1. bucket (string)

Usage

The interface should be familiar to those of you who have used memcache, and should be easy to understand for those of you who haven't.

For example, you can store a string for 2 minutes using EasyCache.set():

EasyCache.set('greeting', 'Hello World!', 2);

You can then retrieve that string with EasyCache.get():

alert(EasyCache.get('greeting'));

You can remove that string from the cache entirely with EasyCache.remove():

EasyCache.remove('greeting');

You can remove all items from the cache entirely with EasyCache.flush():

EasyCache.flush();

You can remove only expired items from the cache entirely with EasyCache.flushExpired():

EasyCache.flushExpired();

Returns whether local storage is supported.:

alert(EasyCache.supported());

The library also takes care of serializing objects, so you can store more complex data:

EasyCache.set('data', {'name': 'Hemn', 'age': 26}, 2);

And then when you retrieve it, you will get it back as an object:

alert(EasyCache.get('data').name);

If you have multiple instances of EasyCache running on the same domain, you can partition data in a certain bucket via:

EasyCache.set('response', '...', 2);
EasyCache.setBucket('lib');
EasyCache.set('path', '...', 2);
EasyCache.flush(); // Only removes 'path' which was set in the lib bucket
EasyCache.resetBucket();
EasyCache.flush(); // Remove all EasyCache items and expiry markers without affecting rest of localStorage

For more live examples, play around with the demo here: http://iprodev.github.io/JS-EasyCache/demo.html

Real-World Usage

This library was originally developed with the use case of caching results of JSON API queries to speed up my webapps and give them better protection against flaky APIs.

For example use EasyCache to fetch Youtube API results for 10 minutes:

var key = 'youtube:' + query;
var json = EasyCache.get(key);
if (json) {
  processJSON(json);
} else {
  fetchJSON(query);
}

function processJSON(json) {
  // ..
}

function fetchJSON() {
  var searchUrl = 'http://gdata.youtube.com/feeds/api/videos';
  var params = {
   'v': '2', 'alt': 'jsonc', 'q': encodeURIComponent(query)
  }
  JSONP.get(searchUrl, params, null, function(json) {
    processJSON(json);
    EasyCache.set(key, json, 10);
  });
}

It does not have to be used for only expiration-based caching, however. It can also be used as just a wrapper for localStorage, as it provides the benefit of handling JS object (de-)serialization.

Browser Support

The EasyCache library should work in all browsers where localStorage is supported. A list of those is here: http://caniuse.com/#search=localstorage

Credits

JS-EasyCache was created by Hemn Chawroka from iProDev. Released under the MIT license.