jquery/src/data.js

var expando = "jQuery" + now(), uuid = 0, windowData = {};
var emptyObject = {};

jQuery.extend({
	cache: {},
	
	expando:expando,

	data: function( elem, name, data ) {
		elem = elem == window ?
			windowData :
			elem;

		var id = elem[ expando ], cache = jQuery.cache, thisCache;

		// Handle the case where there's no name immediately
		if ( !name && !id ) {
			return null;
		}

		// Compute a unique ID for the element
		if ( !id ) { 
			id = ++uuid;
		}

		// Avoid generating a new cache unless none exists and we
		// want to manipulate it.
		if ( cache[ id ] ) {
			thisCache = cache[ id ];
		} else if ( typeof data === "undefined" ) {
			thisCache = emptyObject;
		} else {
			thisCache = cache[ id ] = {};
		}
		
		// Prevent overriding the named cache with undefined values
		if ( data !== undefined ) {
			elem[ expando ] = id;
			thisCache[ name ] = data;
		}
		
		return name ? thisCache[ name ] : thisCache;
	},

	removeData: function( elem, name ) {
		elem = elem == window ?
			windowData :
			elem;

		var id = elem[ expando ], cache = jQuery.cache, thisCache = cache[ id ];

		// If we want to remove a specific section of the element's data
		if ( name ) {
			if ( thisCache ) {
				// Remove the section of cache data
				delete thisCache[ name ];

				// If we've removed all the data, remove the element's cache
				if ( jQuery.isEmptyObject(thisCache) ) {
					jQuery.removeData( elem );
				}
			}

		// Otherwise, we want to remove all of the element's data
		} else {
			// Clean up the element expando
			try {
				delete elem[ expando ];
			} catch( e ) {
				// IE has trouble directly removing the expando
				// but it's ok with using removeAttribute
				if ( elem.removeAttribute ) {
					elem.removeAttribute( expando );
				}
			}

			// Completely remove the data cache
			delete cache[ id ];
		}
	}
});

jQuery.fn.extend({
	data: function( key, value ){
		if ( typeof key === "undefined" && this.length ) {
			return jQuery.data( this[0] );
		}

		var parts = key.split(".");
		parts[1] = parts[1] ? "." + parts[1] : "";

		if ( value === undefined ) {
			var data = this.triggerHandler("getData" + parts[1] + "!", [parts[0]]);

			if ( data === undefined && this.length ) {
				data = jQuery.data( this[0], key );
			}
			return data === undefined && parts[1] ?
				this.data( parts[0] ) :
				data;
		} else {
			return this.trigger("setData" + parts[1] + "!", [parts[0], value]).each(function(){
				jQuery.data( this, key, value );
			});
		}
	},

	removeData: function( key ){
		return this.each(function(){
			jQuery.removeData( this, key );
		});
	}
});