persistentobject/PersistentObjectStore.js

.pragma library

function getDatabase() {
	return openDatabaseSync("SettingsDB", "1.0", "Settings", 5000);
}

function initialize() {
	var db = getDatabase();
	db.transaction(
		function(tx) {
			// Create the settings table if it doesn't already exist
			// If the table exists, this is skipped
			tx.executeSql('CREATE TABLE IF NOT EXISTS settings(settingsName TEXT, keyName TEXT, value TEXT)');
			tx.executeSql('CREATE INDEX IF NOT EXISTS settingsName ON settings (settingsName);');
			tx.executeSql('CREATE UNIQUE INDEX IF NOT EXISTS fullKeyName ON settings (settingsName, keyName);');
		}
	);
	console.log('DB initialized');
}

function save(obj) {
	var db = getDatabase();
	db.transaction(
		function (tx) {
			// Clean all fields of this settings object first, so the DB is always clean from unused fields
			tx.executeSql('DELETE FROM settings WHERE settingsName=?;', [obj.objectName]);

			// Save all fields
			for (var fieldName in obj) {
				var value = JSON.stringify(obj[fieldName]);
				if (typeof value === 'undefined' || fieldName === 'objectName') {
					continue;
				}

				tx.executeSql('INSERT INTO settings (settingsName, keyName, value) VALUES (?, ?, ?);', [obj.objectName, fieldName, value]);
				console.log("Saved: " + obj.objectName + "." + fieldName + " => " + value);
			}
		}
	);
}

function load(obj) {
	var db = getDatabase();
	db.transaction(
		function (tx) {

			// Load fields
			for (var fieldName in obj) {
				var rs = tx.executeSql('SELECT value FROM settings WHERE settingsName=? AND keyName=?;', [obj.objectName, fieldName]);

				if (rs.rows.length > 0) {
					obj[fieldName] = JSON.parse(rs.rows.item(0).value);
					console.log("Loaded: " + obj.objectName + "." + fieldName + ". New value: " + obj[fieldName]);
				} else {
					console.log("Not loaded: " + obj.objectName + "." + fieldName + ". Current value:" + obj[fieldName]);
				}
			}
		}
	);
}