HTML
<div id="spoiler" style="display: none;">
Texto oculto</div>
<button onclick="if(document.getElementById('spoiler') .style.display=='none') {document.getElementById('spoiler') .style.display=''}else{document.getElementById('spoiler') .style.display='none'}"
title="Click to show/hide" type="button">Abrir/Cerrar</button>
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