The SpeechSynthesisUtterance interface of the Web Speech API represents a speech request. It contains the content the speech service should read and information about how to read it (e.g. language, pitch and volume.)

SpeechSynthesisUtterance()

Returns a new SpeechSynthesisUtterance object instance.

SpeechSynthesisUtterance also inherits properties from its parent interface, EventTarget.

SpeechSynthesisUtterance.lang

Gets and sets the language of the utterance.

SpeechSynthesisUtterance.pitch

Gets and sets the pitch at which the utterance will be spoken at.

SpeechSynthesisUtterance.rate

Gets and sets the speed at which the utterance will be spoken at.

SpeechSynthesisUtterance.text

Gets and sets the text that will be synthesized when the utterance is spoken.

SpeechSynthesisUtterance.voice

Gets and sets the voice that will be used to speak the utterance.

SpeechSynthesisUtterance.volume

Gets and sets the volume that the utterance will be spoken at.

Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.

boundary

Fired when the spoken utterance reaches a word or sentence boundary. Also available via the onboundary property.

end

Fired when the utterance has finished being spoken. Also available via the onend property.

error

Fired when an error occurs that prevents the utterance from being successfully spoken. Also available via the onerror property

mark

Fired when the spoken utterance reaches a named SSML "mark" tag. Also available via the onmark property.

pause

Fired when the utterance is paused part way through. Also available via the onpause property.

resume

Fired when a paused utterance is resumed. Also available via the onresume property.

start

Fired when the utterance has begun to be spoken. Also available via the onstart property.

In our basic Speech synthesizer demo, we first grab a reference to the SpeechSynthesis controller using window.speechSynthesis. After defining some necessary variables, we retrieve a list of the voices available using SpeechSynthesis.getVoices() and populate a select menu with them so the user can choose what voice they want.

Inside the inputForm.onsubmit handler, we stop the form submitting with preventDefault(), use the constructor to create a new utterance instance containing the text from the text <input>, set the utterance's voice to the voice selected in the <select> element, and start the utterance speaking via the SpeechSynthesis.speak() method.

const synth = window.speechSynthesis;

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

let voices;

function loadVoices() {
  voices = synth.getVoices();
  for (let i = 0; i < voices.length; i++) {
    const option = document.createElement("option");
    option.textContent = `${voices[i].name} (${voices[i].lang})`;
    option.value = i;
    voiceSelect.appendChild(option);
  }
}

// in Google Chrome the voices are not ready on page load
if ("onvoiceschanged" in synth) {
  synth.onvoiceschanged = loadVoices;
} else {
  loadVoices();
}

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

  const utterThis = new SpeechSynthesisUtterance(inputTxt.value);
  utterThis.voice = voices[voiceSelect.value];
  synth.speak(utterThis);
  inputTxt.blur();
};

• Web Speech API