JSFiddle - React, Tailwind, and code Playground

HTML

<div data-bind="foreach: ages">
  <input type="number" data-bind="value: age" />
  <span data-bind="text: age"></span>
    <br/>
</div>

JavaScript

var model = function() {
  this.ages = ko.observableArray([
      {age: ko.observable(13).extend({defaultIfBlank: "0"})},
      {age: ko.observable(18).extend({defaultIfBlank: "0"})},
      {age: ko.observable(16).extend({defaultIfBlank: "0"})},
      {age: ko.observable(13).extend({defaultIfBlank: "0"})}
  ]);
};

ko.applyBindings(new model());