<button id="btn">ダブルクリック！</button>
*{
  text-align:center;
}

#btn{
  margin-top:20px;
}
const btn = document.getElementById('btn');

btn.addEventListener('dblclick',function(){
  this.insertAdjacentHTML('afterend', '<p>ダブルクリックされました</p>');
})

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External JavaScript

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