IBAN

The account number, with the mod 97 check applied: it is the only thing that catches a digit changed while typing, which is the real error. As you type it is split into groups of four, as it comes printed by the bank; what comes out through onChange has no spaces and is in uppercase, which is what gets stored.

When to use it

• Direct debits, refunds by transfer, a supplier's payment details.
• error for whatever the server says: it takes precedence over the one the field computes.

When not to

• Showing an account that is not edited, with its copy button: Copyable.
• A NIF, a NIE or a CIF: DocumentField.

Keyboard: that of a text field; you can paste with or without spaces. The check runs when leaving the field, not on every key.

Accessibility: it is a TextField, with its label (by default "IBAN"), its help text and its error linked. When the account checks out, the help text says so in words: "Account is valid". The error explains what is wrong: that it does not start with the two country letters and two digits, or that the number is not valid.

Fine-tuning: no variables of its own: they are those of the field, --amset-field-*, with digits in a fixed width (amset-field--numeric).