JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://cdnjs.cloudflare.com/ajax/libs/knockout/2.2.1/knockout-min.js"></script>
simple text area input
<br/>
<textarea rows="5" type="text" data-bind="value:function(data){return SetValue(data);}" />

JavaScript

function AppModel() {
    this.firstName = "ebram";
    this.lastName = "Tharwat";
    this.SetValue = function (data) {
        return data.toUpperCase();
    }
}
ko.applyBindings(new AppModel());