christian-beckmann / sessioncache

A localStorage-based memcache-inspired client-side caching library.

sessioncache

This is a simple library that emulates memcache functions using HTML5 sessionStorage, so that you can cache data on the client and associate an expiration time with each piece of data. If the sessionStorage limit (~10MB) is exceeded, it tries to create space by removing the items that are closest to expiring anyway. If sessionStorage is not available at all in the browser, the library degrades by simply not caching and all cache requests return null.

Methods

The library exposes 5 methods: set(), get(), remove(), flush(), and setBucket().

---

sessioncache.set

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

Arguments

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

---

sessioncache.get

Retrieves specified value from sessionStorage, if not expired.

Arguments

1. key (string)

Returns

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

---

sessioncache.remove

Removes a value from sessionStorage.

Arguments

1. key (string)

---

sessioncache.flush

Removes all sessioncache items from sessionStorage without affecting other data.

---

sessioncache.setBucket

Appends CACHE_PREFIX so sessioncache 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 sessioncache.set():

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

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

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

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

sessioncache.remove('greeting');

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

sessioncache.flush();

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

sessioncache.flushExpired();

You can also check if local storage is supported in the current browser with sessioncache.supported():

if (!sessioncache.supported()) {
  alert('Local storage is unsupported in this browser');
  return;
}

You can enable console warning if set fails with sessioncache.enableWarnings():

// enable warnings
sessioncache.enableWarnings(true);

// disable warnings
sessioncache.enableWarnings(false);

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

sessioncache.set('data', {'name': 'Pamela', 'age': 26}, 2);

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

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

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

sessioncache.set('response', '...', 2);
sessioncache.setBucket('lib');
sessioncache.set('path', '...', 2);
sessioncache.flush(); //only removes 'path' which was set in the lib bucket

For more live examples, play around with the demo here: http://pamelafox.github.com/sessioncache/demo.html

Browser Support

The sessioncache library should work in all browsers where sessionStorage is supported. A list of those is here: http://caniuse.com/#feat=namevalue-storage

Further docs: https://developer.mozilla.org/en-US/docs/Web/API/Web_Storage_API