JSFiddle - React, Tailwind, and code Playground

HTML

<p>First name:<input data-bind="value: firstName" /></p>
<p>Last name:<input data-bind="value: lastName" /></p>
<p>Full name:<span data-bind="text: fullName"></span></p>

JavaScript

function AppViewModel() {
  this.firstName = ko.observable("Taro");
  this.lastName = ko.observable("Yamada");

  this.fullName = ko.computed(function() {
    return this.firstName() + " " + this.lastName();
  }, this);
}

// Activates knockout.js
ko.applyBindings(new AppViewModel());