TextFormat: rangeStart property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The rangeStart property of the TextFormat interface indicates the start position of the text range that needs to be formatted with the given text format.



Reading the range of text that needs to be formatted

The following example shows how to use the textformatupdate event's rangeStart and rangeEnd properties to determine the range of text that needs to be formatted. Note that the event listener callback in this example is only called when using an IME window to compose text.

<div id="editor" style="height:200px;background:#eee;"></div>
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) {
      `IME wants to apply formatting between ${format.rangeStart} and ${format.rangeEnd}.`,


EditContext API
# dom-textformat-rangestart

Browser compatibility

BCD tables only load in the browser

See also