JSFiddle - React, Tailwind, and code Playground
HTML
<div id="container"></div>
CSS
.main {
width: 500px;
height: 300px;
border: 1px solid blue;
}
JavaScript
document.getElementById("container").classList.add("main");
<div id="container"></div>
.main {
width: 500px;
height: 300px;
border: 1px solid blue;
}
document.getElementById("container").classList.add("main");