JSFiddle - React, Tailwind, and code Playground

HTML

<div id="vm"> 
    <h2>The title is: <span data-bind="text: title"></span></h2>
    <h2>The length is: <span data-bind="text: title.length"></span></h2>
    <h2>Length from computed: <span data-bind="text: titleLength"></span></h2>
    <input data-bind="value: title, valueUpdate: 'keyup'"/>
  </div>

JavaScript

function VM() {
    var self = this;
    self.title = ko.observable();
    self.titleLength = ko.computed(function() {
        return self.title.length;
    });
}
ko.applyBindings(VM(), document.getElementById('vm'));