SpeechSynthesisVoice: localService property

The localService read-only property of the SpeechSynthesisVoice interface returns a boolean value indicating whether the voice is supplied by a local speech synthesizer service (true), or a remote speech synthesizer service (false.)

This property is provided to allow differentiation in the case that some voice options are provided by a remote service; it is possible that remote voices might have extra latency, bandwidth or cost associated with them, so such distinction may be useful.

for (let i = 0; i < voices.length; i++) {
  const option = document.createElement("option");
  option.textContent = `${voices[i].name} (${voices[i].lang})`;

  if (voices[i].default) {
    option.textContent += " — DEFAULT";
  }

  console.log(voices[i].localService);

  option.setAttribute("data-lang", voices[i].lang);
  option.setAttribute("data-name", voices[i].name);
  voiceSelect.appendChild(option);
}