HTMLInputElement: select イベント

addEventListener("select", (event) => {});
onselect = (event) => {};

<input value="この要素のテキストの一部を選択してみてください。" />
<p id="log"></p>

function logSelection(event) {
  const log = document.getElementById("log");
  const selection = event.target.value.substring(
    event.target.selectionStart,
    event.target.selectionEnd,
  );
  log.textContent = `You selected: ${selection}`;
}
const input = document.querySelector("input");
input.addEventListener("select", logSelection);

input.onselect = logSelection;