JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://github.com/SteveSanderson/knockout/raw/master/build/output/knockout-latest.debug.js"></script>
<script src="https://github.com/jquery/jquery-tmpl/raw/master/jquery.tmpl.js"></script>
<script src="https://github.com/SteveSanderson/knockout.mapping/raw/master/build/output/knockout.mapping-latest.debug.js"></script>
<p data-bind="text: propertyOne"></p>
<p data-bind="text: propertyTwo"></p>
<input type="button" value="Update model" data-bind="click: updateMe"/>

JavaScript

var CompositeModel = {
 propertyOne: 'hi',
 propertyTwo: 'there'
};

var newCompositeModel = {
 propertyOne: 'how are',
 propertyTwo: 'you?'
};

var viewModel = ko.mapping.fromJS(CompositeModel);

viewModel.updateMe = function() {ko.mapping.fromJS(newCompositeModel, viewModel)}
ko.applyBindings(viewModel);