gistfile1.js

// idbsimple - tiny wrapper around indexeDB to behave like an
// asynchronous localStorage.

// API (all callbacks are optional):
// idbsimple.getItem(key, function(error, value){...});
// idbsimple.setItem(key, value, function(error){...});
// idbsimple.removeItem(key, function(error){...});
// idbsimple.clear(function(error){...});
// idbsimple.delete();

(function(window){

var _STATUS = { NOT_OPEN: 1, OPENING: 2, OPEN: 4, FAILED: 8 },
	databaseName = 'SimpleIDB',
	storeName = 'values',
	db = null,
	queue = [],
	indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB,
	status = indexedDB ? _STATUS.NOT_OPEN : _STATUS.FAILED;

var execQueue = function() {
	for( var i = 0; i < queue.length; i++ ) {
		queue[i]();
	}
	queue = [];
};

var exec = function(mode, action, callback, params) {
	if( status === _STATUS.OPEN ) {
		var store = db.transaction(storeName, mode).objectStore(storeName);
		var req = store[action].apply(store, params);

		if( callback ) {
			req.onsuccess = function(){
				callback(null, req.result);
			};
			req.onerror = function(){
				callback(req.error, null);
			};
		}
	}
	else if( status === _STATUS.NOT_OPEN || status === _STATUS.OPENING ) {
		queue.push( exec.bind(this, mode, action, callback, params) );

		if( status === _STATUS.NOT_OPEN ) {
			var req = indexedDB.open(databaseName);

			req.onupgradeneeded = function() {
				req.result.createObjectStore(storeName);
			};

			req.onsuccess = function() {
				status = _STATUS.OPEN;
				db = req.result;
				execQueue();
			};

			req.onerror = function() {
				status = _STATUS.FAILED;
				execQueue();
			};
		}
	}
	else if( this.status === _STATUS.FAILED && callback ) {
		callback(status);
	}
};

window.idbsimple = {
	'getItem': function(key, callback) {
		exec('readonly', 'get', callback, [key]);
	},
	'setItem': function(key, value, callback) {
		exec('readwrite', 'put', callback, [value, key]);
	},
	'removeItem': function(key, callback) {
		exec('readwrite', 'delete', callback, [key]);
	},
	'clear': function(callback) {
		exec('readwrite', 'clear', callback, []);
	},
	'delete': function() {
		if( indexedDB ) {
			status = _STATUS.NOT_OPEN;
			indexedDB.deleteDatabase(databaseName);
		}
	}
};

})(window);