cache.js

/* from
   http://www.bennadel.com/blog/2105-Exploring-HTML5-s-localStorage-Persistent-Client-Side-Key-Value-Pairs.htm */

function Cache( nativeStorage, serializer ){
 
	// Store the native storage reference as the object that
	// we are going to proxy. This object must uphold the
	// HTML5 Storage interface.
	this.storage = nativeStorage;
    
	// Store the serialization behavior. This object must
	// uphold the JSON interface for serialization and
	// deserialization.
	this.serializer = serializer;
}
 
 
// Set up the class methods.
Cache.prototype = {
    
	// I clear the cache.
	clear: function(){
		// Clear the storage container.
		this.storage.clear();
        
		// Return this object reference for method chaining.
		return( this );
	},
    
    
	// I get an item from the cache. If the item cannot be
	// found, I can pass back an optional default value.
	getItem: function( key, defaultValue ){
		// Get the cached item.
		var value = this.storage.getItem( key );
        
		// Check to see if it exists. If it does, then we
		// need to deserialize it.
		if (value == null){
            
			// No cached item could be found. Now, we either
			// have to return the default value, or we have
			// to return Null. We have to be careful here,
			// though, because the default value might be a
			// falsy.
			return(
				(typeof( defaultValue ) != "undefined") ?
					defaultValue :
					null
			);
            
		} else {
            
			// The value was found; return it in its
			// original form.
			return(
				this.serializer.parse( value )
			);
            
				}
	},
    
    
	// I check to see if the given key exists in the storage
	// container.
	hasItem: function( key ){
		// Simply check to see if the key access results in a
		// null value.
		return(
			this.storage.getItem( key ) != null
		);
	},
    
    
	// I remove the given item from the cache.
	removeItem: function( key ){
		// Remove the key from the storage container.
		this.storage.removeItem( key );
        
		// Return this object reference for method chaining.
		return( this );
	},
    
    
	// I store the item in the cache. When doing this, I
	// automatically serialize the value.
	//
	// NOTE: Not all value (ex. functions and private
	// variables) will serialize.
	setItem: function( key, value ){
		// Store the serialize value.
		this.storage.setItem(
			key,
			this.serializer.stringify( value )
		);
        
		// Return this object reference for method chaining.
		return( this );
	},

    setDefault: function(key, value) {
        this.setItem(key, this.getItem(key, value))
        return this
    }
    
};


// Now, let's create an instance of our new cache. When doing
// this, we're going to use localStorage as our storage
// container and the native JSON object as our serializer.
var cache = new Cache( localStorage, JSON );