JSFiddle - React, Tailwind, and code Playground

HTML

<div id="teste">Um <strong>texto</strong> <em>qualquer</em>.</div>
<button>Copiar</button>

JavaScript

document.querySelector("button").onclick = function() {
    var divACopiar = document.querySelector("#teste");
    
    var range = document.createRange();
    range.selectNode(divACopiar);
    window.getSelection().addRange(range);
    document.execCommand("copy");
};