ValidityState
The validity states that an element can be in, with respect to constraint validation. Together, they help explain why an element's value fails to validate, if it's not valid.
interface ValidityState {
readonly badInput: boolean;
readonly customError: boolean;
readonly patternMismatch: boolean;
readonly rangeOverflow: boolean;
readonly rangeUnderflow: boolean;
readonly stepMismatch: boolean;
readonly tooLong: boolean;
readonly tooShort: boolean;
readonly typeMismatch: boolean;
readonly valid: boolean;
readonly valueMissing: boolean;
}var ValidityState: {
prototype: ValidityState;
new (): ValidityState;
};