JSFiddle - React, Tailwind, and code Playground

by orlov0562

HTML

<div id="summ">0</div>
<button id="dec">-1</button>
<button id="inc">+1</button>

JavaScript

var summEl = document.getElementById('summ');
var summChangedEvent = new Event('summChanged');

summEl.addEventListener('summChanged', function (e) {
	summEl.style.fontSize = (+summEl.innerHTML > 3) ? '2em' : '1em';
}, false);

document.getElementById('inc').addEventListener('click', function (e) {
	summEl.innerHTML = +summEl.innerHTML + 1;
	summEl.dispatchEvent(summChangedEvent);
}, false);

document.getElementById('dec').addEventListener('click', function (e) {
	summEl.innerHTML = +summEl.innerHTML - 1;
	summEl.dispatchEvent(summChangedEvent);
}, false);