JSFiddle - React, Tailwind, and code Playground

HTML

<div data-bind="style: fontSizeCSS">
    <p>Lorem ipsum</p>
</div>

JavaScript

function ViewModel() {
    this.fontSize = ko.observable(42);

    this.fontSizeCSS = ko.computed(function() {
        return {"font-size": this.fontSize() + "px"};
    }, this);

}

// Activates knockout.js
ko.applyBindings(new ViewModel());