JSFiddle - React, Tailwind, and code Playground

HTML

<input data-bind="value: FirstName()">
<input data-bind="value: LastName">
<label data-bind="text: FullName"></label>

JavaScript

var Person = function(data){
    var self = this;
    self.FirstName = ko.observable(data.FirstName);
    self.LastName  = ko.observable(data.LastName);
    self.FullName = ko.computed(function(){
        return self.FirstName() + " " + self.LastName()
    });
}
myData = { FirstName: "John", LastName: "Smith" }
var me = new Person(myData);

ko.applyBindings(me);