HTMLDialogElement: cancel event

addEventListener("cancel", (event) => { })

oncancel = (event) => { }

<dialog id="dialog">
  <button type="button" id="request-close">Request Close</button>
</dialog>

<button id="open">Open dialog</button>

<pre id="log"></pre>

#log {
  height: 170px;
  overflow: scroll;
  padding: 0.5rem;
  border: 1px solid black;
}

const logElement = document.getElementById("log");
function log(text, clear = false) {
  if (clear) {
    logElement.innerText = "";
  }
  logElement.innerText = `${logElement.innerText}${text}\n`;
  logElement.scrollTop = logElement.scrollHeight;
}

const dialog = document.getElementById("dialog");
const openButton = document.getElementById("open");
const requestCloseButton = document.getElementById("request-close");

// Open button opens a modal dialog
openButton.addEventListener("click", () => {
  log("open button click event fired", true);
  log("dialog showModal() called");
  dialog.showModal();
});

// Request close
requestCloseButton.addEventListener("click", () => {
  log("request close button click event fired");
  log("dialog requestClose() called");
  // Triggers the cancel event
  dialog.requestClose();
});

// Fired when requestClose() is called
// Prevent the dialog from closing by calling event.preventDefault()
dialog.addEventListener("cancel", (event) => {
  log("dialog cancel event fired");
  // Uncomment the next two lines to prevent the dialog from closing
  // log("dialog close cancelled");
  // event.preventDefault();
});

dialog.addEventListener("close", (event) => {
  log("dialog close event fired");
});