JSFiddle - React, Tailwind, and code Playground

HTML

<div class="disable-select" data-content="456"></div>

CSS

.disable-select:after {
  content: attr(data-content);
}

JavaScript

var a = 6;
setTimeout(function () {
    alert(a);
    a = 666;
}, 1000);
a = 66
alert('123456')