JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://afarkas.github.io/lazysizes/lazysizes.min.js"></script>
<button onclick="fn()">add image</button>
<br>
<img data-src="http://lorempixel.com/400/200/" class="lazyload" />

CSS

button {
  display: inline-block;
  border: none;
  background: purple;
  color: white;
  padding: 6px 15px;
  font-size: 20px;
  margin-bottom: 10px;
}

img {
  width: 19%;
  height: auto;
  float: left;
  display: block;
  margin: .5%;
}

JavaScript

function fn() {
  var img = document.createElement('img');
  img.setAttribute('data-src', 'http://lorempixel.com/400/200/')
  img.className = 'lazyload';
  document.body.appendChild(img);
}
fn();