InputEvent: свойство inputType

<p id="log">Input type:</p>
<div
  contenteditable="true"
  style="margin: 20px;padding: 20px;border:2px dashed red;">
  <p>
    Some sample text. Try inserting line breaks, or deleting text in different
    ways, or pasting different content in.
  </p>
  <hr />
  <ul>
    <li>A sample</li>
    <li>bulleted</li>
    <li>list.</li>
  </ul>
  <p>Another paragraph.</p>
</div>

const log = document.getElementById("log");
const editable = document.querySelector("div[contenteditable]");
editable.addEventListener("input", logInputType);

function logInputType(event) {
  log.textContent = `Input type: ${event.inputType}`;
}