JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://cdnjs.cloudflare.com/ajax/libs/knockout-validation/1.0.2/knockout.validation.min.js"></script>
<p>First name:
    <input data-bind="value: person().firstName" />
</p>
<button data-bind="click: changePerson">Change Person</button>

CSS

.input-validation-error {
    border: solid 1px red !important
}

JavaScript

var ViewModel = function (first) {
     this.person = ko.observable(new Person(first));

     this.changePerson = function () {
         this.person(new Person("changed"));
     };
 };

 var Person = function (first) {
     this.firstName = ko.observable(first).extend({
         required: true
     });
 };

 ko.validation.init({
     decorateElement: true,
     errorElementClass: "input-validation-error"
 },
 true);

 ko.applyBindings(new ViewModel("Planet"));