JSFiddle - React, Tailwind, and code Playground
HTML
<!DOCTYPE html>
<html>
<head></head>
<body>
<textarea id="iptDetalhesCopia"></textarea>
<input onkeyup="FuncaoTeste( this.value )" type="text" class="form-control" id="iptDetalhes" placeholder="Digite aqui">
</body>
</html>JavaScript
function FuncaoTeste( e ) {
document.getElementById( 'iptDetalhesCopia' ).value = e;
}