JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://raw.github.com/SteveSanderson/knockout.mapping/master/build/output/knockout.mapping-latest.debug.js"></script>
<input type="text" id="txtFName" data-bind="value: firstName" class="input-small" >
<input type="text" id="txtLName" data-bind="value: lastName" class="input-small">

JavaScript

var user = {"firstName":"Test","lastName":"Test Last"};
    var viewModel = ko.mapping.fromJS(user);
    ko.applyBindings(viewModel);