JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.aspnetcdn.com/ajax/knockout/knockout-3.0.0.js"></script>
<div data-bind="foreach: ids" class="">
    <label>                      
        <input type="radio"  name="someid" data-bind="value: value, checked: $root.selectedid" />
        <span data-bind="text: text"></span>
    </label>
</div>
<br/>
<input type="button" data-bind="click: test1" value="Test1"/>
<input type="button" data-bind="click: test2" value="Test2"/>
<input type="button" data-bind="click: test3" value="Test3"/>

JavaScript

function radiodata(text,value){
    this.text = text;
    this.value= value;
}

var viewModel = function(){
    var self = this;
    self.selectedid = ko.observable();
    
    self.ids = ko.observableArray([
        new radiodata('one',1),
        new radiodata('two',2),
        new radiodata('three',3)
         ]);
    self.test1 = function(){
      self.selectedid(2);//this doesnot work
    };
     self.test2 = function(){
      self.selectedid('2');//this works
    };
     self.test3 = function(){
      self.selectedid((3).toString());//this was my hack
    };
}

var model = new viewModel();
ko.applyBindings(model);