transactionStore method
Implementation
Transaction transactionStore(String storeName, String mode) {
if (mode != 'readonly' && mode != 'readwrite') {
throw new ArgumentError(mode);
}
// Try and create a transaction with a string mode. Browsers that expect a
// numeric mode tend to convert the string into a number. This fails
// silently, resulting in zero ('readonly').
return _transaction(storeName, mode);
}