API: Storage StorageEngineHTML5.js (YUI Library)

# Yahoo! UI Library

### Storage 2.8.1

Yahoo! UI Library > Storage > StorageEngineHTML5.js (source view)
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    /*
     * HTML limitations:
     *  - 5MB in FF and Safari, 10MB in IE 8
     *  - only FF 3.5 recovers session storage after a browser crash
     *
     * Thoughts:
     *  - how can we not use cookies to handle session
     */
    (function() {
    	// internal shorthand
    var Y = YAHOO.util,
    	YL = YAHOO.lang,

    	/*
    	 * Required for IE 8 to make synchronous.
    	 */
    	_beginTransaction = function(engine) {
    		if (engine.begin) {engine.begin();}
    	},

    	/*
    	 * Required for IE 8 to make synchronous.
    	 */
    	_commitTransaction = function(engine) {
    		if (engine.commit) {engine.commit();}
    	};

    	/**
    	 * The StorageEngineHTML5 class implements the HTML5 storage engine.
    	 * @namespace YAHOO.util
    	 * @class StorageEngineHTML5
    	 * @constructor
    	 * @extend YAHOO.util.Storage
    	 * @param location {String} Required. The storage location.
    	 * @param conf {Object} Required. A configuration object.
    	 */
    	Y.StorageEngineHTML5 = function(location, conf) {
    		var _this = this;
    		Y.StorageEngineHTML5.superclass.constructor.call(_this, location, Y.StorageEngineHTML5.ENGINE_NAME, conf);// not set, are cookies available
    		_this._engine = window[location];
    		_this.length = _this._engine.length;
    		YL.later(250, _this, function() { // temporary solution so that CE_READY can be subscribed to after this object is created
    			_this.fireEvent(_this.CE_READY);
    		});
    	};

    	YAHOO.lang.extend(Y.StorageEngineHTML5, Y.Storage, {

    		_engine: null,

    		/*
    		 * Implementation to clear the values from the storage engine.
    		 * @see YAHOO.util.Storage._clear
    		 */
    		_clear: function() {
    			var _this = this;
    			if (_this._engine.clear) {
    				_this._engine.clear();
    			}
    			// for FF 3, fixed in FF 3.5
    			else {
    				for (var i = _this.length, key; 0 <= i; i -= 1) {
    					key = _this._key(i);
    					_this._removeItem(key);
    				}
    			}
    		},

    		/*
    		 * Implementation to fetch an item from the storage engine.
    		 * @see YAHOO.util.Storage._getItem
    		 */
    		_getItem: function(key) {
    			var o = this._engine.getItem(key);
    			return YL.isObject(o) ? o.value : o; // for FF 3, fixed in FF 3.5
    		},

    		/*
    		 * Implementation to fetch a key from the storage engine.
    		 * @see YAHOO.util.Storage._key
    		 */
    		_key: function(index) {return this._engine.key(index);},

    		/*
    		 * Implementation to remove an item from the storage engine.
    		 * @see YAHOO.util.Storage._removeItem
    		 */
    		_removeItem: function(key) {
    			var _this = this;
    			_beginTransaction(_this._engine);
    			_this._engine.removeItem(key);
    			_commitTransaction(_this._engine);
    			_this.length = _this._engine.length;
    		},

    		/*
    		 * Implementation to remove an item from the storage engine.
    		 * @see YAHOO.util.Storage._setItem
    		 */
    		_setItem: function(key, value) {
    			var _this = this;

    			try {
    				_beginTransaction(_this._engine);
    				_this._engine.setItem(key, value);
    				_commitTransaction(_this._engine);
    				_this.length = _this._engine.length;
    				return true;
    			}
    			catch (e) {
    				return false;
    			}
    		}
    	}, true);

    	Y.StorageEngineHTML5.ENGINE_NAME = 'html5';
    	Y.StorageEngineHTML5.isAvailable = function() {
    		return window.localStorage;
    	};
        Y.StorageManager.register(Y.StorageEngineHTML5);
    }());

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