RTCDTMFToneChangeEvent: tone property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨March 2020⁩.

The read-only property RTCDTMFToneChangeEvent.tone returns the DTMF character which has just begun to play, or an empty string (""). if all queued tones have finished playing (that is, RTCDTMFSender.toneBuffer is empty).

Value

A string with the DTML character playing, or the empty string.

Example

This example establishes a handler for the tonechange event which updates an element to display the currently playing tone in its content, or, if all tones have played, the string "<none>".

dtmfSender.ontonechange = (ev) => {
  let tone = ev.tone;
  if (tone === "") {
    tone = "&lt;none&gt;";
  }

  document.getElementById("playingTone").innerText = tone;
};