JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdn.firebase.com/js/client/2.2.3/firebase.js"></script>
<pre></pre>

JavaScript

var ref = new Firebase('https://stackoverflow.firebaseio.com/29429529'),
    log = document.getElementsByTagName('pre')[0];


ref.on('value', function(snapshot) { log.innerText += JSON.stringify(snapshot.val())+'\n'; });

function setMessage() {
   var skills = {};
   skills['front-end'] = {js:'momentum'}
   ref.set({ sender: 'puf', time: Date.now() ,skills: skills});
}
function updateMessage() {
   var skills = {};
   skills['back-end'] = {js:'firebase'}
   ref.update({ time: Date.now() });
   ref.child('skills').update({ "back-end": { "js": "firebase" } });
}

ref.remove();
setTimeout(setMessage, 1000);
setTimeout(updateMessage, 3000);