JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://knockoutjs.com/downloads/knockout-3.2.0.js"></script>
   <input  type="radio" data-bind="checked: selectedVal" name="1" value="fixedPrice"/>  Fixed Price
 <input class="hn" type="radio" data-bind="checked: selectedVal" name="1" value="allowBiding"/> Allow Biding

<pre data-bind="text:ko.toJSON($data,null,2)"></pre>

<input type="button" id="button" value="Click Me" />

JavaScript

var onClick = function() {
   $('[type=radio]:not(:checked)')[0].click();  
   // $('[type=radio]:not(:checked)').triggerHandler('click');
};

$('#button').click(onClick);

var ViewModel = function () {
    var self = this;
    self.selectedVal = ko.observable("fixedPrice");
    self.selectedVal.subscribe(function (val) {
       console.log(val)
    });
};

ko.applyBindings(new ViewModel());