JSFiddle - React, Tailwind, and code Playground

HTML

<select data-bind="value: selectedValue">
    <option value="volvo">Volvo</option>
    <option value="saab">Saab</option>
    <option value="mercedes">Mercedes</option>
    <option value="audi">Audi</option>
</select>

<span data-bind="text: selectedValue"></span>
<span data-bind="text: selectedText"></span>

JavaScript

var viewModel = {
};

viewModel.selectedValue = ko.observable();
viewModel.selectedText = ko.computed(function () {
    var elem = document.querySelector("select option[value=" + viewModel.selectedValue() + "]");
    return elem && elem.innerHTML;
});

ko.applyBindings(viewModel);