JSFiddle - React, Tailwind, and code Playground

CSS

.red {
    color: red;
    font-size: 13px;
}
#div {
    font-size: 18px;
    color: burlywood;
}

JavaScript

var el1 = document.createElement('div');
el1.innerHTML = 'Element Div 1';
var el2 = document.createElement('span');
el2.innerHTML = ' - Span Element';
el2.classList.add('red');
document.body.appendChild(el1);
el1.appendChild(el2);
el1.id = "div";

// Code for manipulating the created elements
var div = document.getElementById('div');
alert("div.innerHTML => "+div.innerHTML);
var span = document.getElementsByClassName('red')[0];
alert("span.innerHTML => "+span.innerHTML);
alert("div.id => "+div.id);
alert("span.className => "+span.className);