SpeechSynthesisUtterance.onerror

The onerror property of the SpeechSynthesisUtterance interface represents an event handler that will run when an error occurs that prevents the utterance from being successfully spoken (when the error event fires.)

speechSynthesisUtteranceInstance.onerror = function() { ... };

var synth = window.speechSynthesis;

var inputForm = document.querySelector('form');
var inputTxt = document.querySelector('input');
var voiceSelect = document.querySelector('select');

var voices = synth.getVoices();

  ...

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

  var utterThis = new SpeechSynthesisUtterance(inputTxt.value);
  var selectedOption = voiceSelect.selectedOptions[0].getAttribute('data-name');
  for(i = 0; i < voices.length ; i++) {
    if(voices[i].name === selectedOption) {
      utterThis.voice = voices[i];
    }
  }

  synth.speak(utterThis);

  utterThis.onerror = function(event) {
    console.log('An error has occurred with the speech synthesis: ' + event.error);
  }

  inputTxt.blur();
}

• Web Speech API