Usually the current numericValue of the input.
Information about the conditions under which the validation is occurring.
If an object is returned the value of customValidity will be set
as the element's custom validity, if null or undefined the validity message
will not be updated.
Generated using TypeDoc
Implementations of this function examine the current
numericValueand determine if it is valid or not and if the validity should be reported to the user.Set
customValidityto an empty string to make the input valid.