JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://cdn.ractivejs.org/edge/ractive.js"></script>
<main></main>

CSS

body {
    font-family: 'Helvetica Neue', arial, sans-serif;
    font-weight: 200;
    color: #353535;
}

h1, h2, h3, h4, h5, h6 {
    font-weight: 200;
}

.error {
    color: #d00;
    font-family: monospace;
}

JavaScript

Ractive.components.widget = Ractive.extend({
    template: '<p>{{FOO}} {{BAR}}</p>',
    computed: {
        FOO: '${foo}.toUpperCase()',
        BAR: function () {
            return this.get( 'bar' ).toUpperCase();
        }
    },
    
    oninit: function () {
        // uncomment this line and it works
        this.update();
    }
});

var ractive = new Ractive({
    el: 'main',
    template: '<widget/>',
    data: {
        foo: 'fee fi',
        bar: 'fo fum'
    }
});