Native Rules

Required:

var myObj = ko.observable('').extend({ required: true });

Min:

var myObj = ko.observable('').extend({ min: 2 });

Max:

var myObj = ko.observable('').extend({ max: 99 });

MinLength:

var myObj = ko.observable('').extend({ minLength: 3 });

MaxLength:

var myObj = ko.observable('').extend({ maxLength: 12 });

Pattern:

var myObj = ko.observable('').extend({ pattern: '^[a-z0-9].$' });

Step:

var myObj = ko.observable('').extend({ step: 3 });

Email:

var myObj = ko.observable('').extend({ email: true });

Date:

var myObj = ko.observable('').extend({ date: true });

DateISO:

var myObj = ko.observable('').extend({ dateISO: true });

Number:

var myObj = ko.observable('').extend({ number: true });

Digit:

var myObj = ko.observable('').extend({ digit: true });