slender2_nameEditorId.js

function NameEditor({ instanceIndex }) {
  return `
    <div class="nameEditor">
      <div>Enter you name:</div>
      <input onKeyUp="NameEditor.onKeyUp(this, ${instanceIndex})" />
      <div>
        Hello, <span id="nameEditor__name-${instanceIndex}"></span>
      </div>
    </div>
  `;
}

NameEditor.onKeyUp = (input, instanceIndex) => {
  document.getElementById(`nameEditor__name-${instanceIndex}`).innerText = input.value;
};