JSFiddle - React, Tailwind, and code Playground

HTML

<input data-bind="value: myName, valueUpdate:'afterkeydown'" type="text" /><br />
<span  data-bind="text: myNameShown, visible: showWelcome" id="spName"></span>

JavaScript

var model = {
    myName: ko.observable("Bill Gates")
};

model.myNameShown = ko.dependentObservable(function () {
    return "Welcome: " + model.myName();
}, model);

model.showWelcome = ko.dependentObservable(function () {
    return model.myName() && model.myName().trim() != "";
}, model);

ko.applyBindings(model);