Variable: addValidationRule()

const addValidationRule: (element, rule, uniqueName?) => void = Validator.addCustomRule

Adds a custom validation callback for an element. Multiple callbacks can be registered under distinct uniqueName keys.

Parameters

Target element or array-like collection (first element is used).

HTMLElement | ArrayLike<HTMLElement>

(input) => string

Callback returning an error message string when invalid, or null/undefined when valid.

string

Optional key to allow independent removal; defaults to "".

void