Knockout Validation

HTML

<script src="http://ajax.aspnetcdn.com/ajax/knockout/knockout-2.2.1.debug.js"></script>
<script src="https://raw.github.com/ericmbarnard/Knockout-Validation/master/Src/knockout.validation.js"></script>
<script src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.9.1.js"></script>
vm required<input data-bind="value: num1, valueUpdate: 'afterkeydown'"/><br/>
HTML5 required<input required="true" data-bind="value: num2, valueUpdate: 'afterkeydown'" /><br/>
num1 isValid: <span data-bind="text: num1.isValid()"></span><br/>
num2 isValid: <span data-bind="text: num2.isValid()"></span>
<p data-bind="text:ko.toJSON($root)"></p>

CSS

.validationMessage { color: Red; }

JavaScript

ko.validation.init( {parseInputAttributes: true, writeInputAttributes: true} ); //enable HTML5 validation, write HTML5 validation attributes to the controls

var viewModel = {
    num1: ko.observable("1").extend({ required: true }),
    num2: ko.observable("2")
};
ko.applyBindings(viewModel);
//debugger;