SpeechSynthesisErrorEvent

const synth = window.speechSynthesis;

const inputForm = document.querySelector("form");
const inputTxt = document.querySelector("input");
const voiceSelect = document.querySelector("select");

const voices = synth.getVoices();

// …

inputForm.onsubmit = (event) => {
  event.preventDefault();

  const utterThis = new SpeechSynthesisUtterance(inputTxt.value);
  const selectedOption =
    voiceSelect.selectedOptions[0].getAttribute("data-name");
  for (const voice of voices) {
    if (voice.name === selectedOption) {
      utterThis.voice = voice;
    }
  }

  synth.speak(utterThis);

  utterThis.onerror = (event) => {
    console.log(
      `An error has occurred with the speech synthesis: ${event.error}`,
    );
  };

  inputTxt.blur();
};