phoneGap HTML5 SQLite database schema migration example

//phoneGap HTML5 SQLite database schema migration example
var db = null;
var current_migration = null;
var current_schema_version = null;

// keep migration version order
var db_migrations = {
  v1: {
    version: "1.0",
    up: function(tx) {
      tx.executeSql('CREATE TABLE IF NOT EXISTS food (id INTEGER AUTOINCREMENT PRIMARY KEY, food_list_type SMALLINT, name VARCHAR(255));');
    },
    down: function(tx) {
      tx.executeSql('DROP TABLE IF EXISTS food;');
    },
  },

  v2: {
    version: "2.0",
    up: function(tx) {
      tx.executeSql('CREATE TABLE IF NOT EXISTS food_notes (food_id INTEGER NOT NULL, note TEXT, picture VARCHAR(255));');
      tx.executeSql('CREATE INDEX IF NOT EXISTS food_notes_food_id_idx ON food_notes(food_id);');

      tx.executeSql('CREATE TABLE IF NOT EXISTS food_in_food (food_id INTEGER NOT NULL, paremt_id INTEGER NOT NULL);');
      tx.executeSql('CREATE INDEX IF NOT EXISTS food_in_food_id_idx ON food_in_food(food_id);');
      tx.executeSql('CREATE UNIQUE INDEX IF NOT EXISTS food_in_food_uniq_idx ON food_in_food(paremt_id,food_id);');

    },
    down: function(tx) {
      tx.executeSql('DROP INDEX IF EXISTS food_notes_food_id_idx;');
      tx.executeSql('DROP TABLE IF EXISTS food_notes;');

      tx.executeSql('DROP INDEX IF EXISTS food_in_food_id_idx;');
      tx.executeSql('DROP INDEX IF EXISTS food_in_food_uniq_idx;');
      tx.executeSql('DROP TABLE IF EXISTS food_in_food;');
    },
  },

};

function createDB(name,displayName, size) {
  db = window.openDatabase(name, "", displayName, size);
  for(m in db_migrations) {
    current_migration = db_migrations[m];
    if (db.version < current_migration.version) {
      db.transaction(current_migration.up, createDBError, createDBSuccess);
    }
  }
}

function createDBSuccess() {
  current_schema_version = current_migration.version;
  db.changeVersion(db.version,current_schema_version);
}

function createDBError(err) {
  navigator.notification.alert('Error updating '+db.version+' database: '+err.message);
  db.transaction(current_migration.down,createDBErrorFatal,createDBSuccessAll);
}


function createDBErrorFatal(err) {
  navigator.notification.alert('Fatal Error when rollback '+current_migration.version+' database: '+err.message);
}

function createDBSuccessAll() {
  navigator.notification.alert('Database rollback from '+current_migration.version+' version');
}