TextFormat: rangeStart property

<div id="editor"></div>

#editor {
  height: 200px;
  background: #eeeeee;
}

const editorEl = document.getElementById("editor");
const editContext = new EditContext(editorEl);
editorEl.editContext = editContext;
editContext.addEventListener("textformatupdate", (e) => {
  const formats = e.getTextFormats();
  for (const format of formats) {
    console.log(
      `IME wants to apply formatting between ${format.rangeStart} and ${format.rangeEnd}.`,
    );
  }
});