JSFiddle - React, Tailwind, and code Playground

HTML

<html>
    <head>
        <script src="http://cloud.github.com/downloads/SteveSanderson/knockout/knockout-2.1.0.js" ></script>
    </head>
    <body>
        <div data-bind="text: onString"></div>
        <div id="test"></div>
    </body>
</html>

JavaScript

function MyData() {
  var self = this;
  self.currentOnOf = ko.observable(1);
  self.available = ko.observableArray();
  self.onString = ko.computed(function () {
    return "On " + self.currentOnOf() + " of " + self.available ().length;}, self);
}

var data = new MyData();

$(document).ready(function () {
    ko.applyBindings(data);
    data.available().push(1);
    data.available().push(2);
    $("#test").html(data.available().length);
});