The SpeechSynthesis interface of the Web Speech API is the controller interface for the speech service; this can be used to retrieve information about the synthesis voices available on the device, start and pause speech, and other commands besides.

SpeechSynthesis also inherits properties from its parent interface, EventTarget.

SpeechSynthesis.paused Read only

A boolean value that returns true if the SpeechSynthesis object is in a paused state.

SpeechSynthesis.pending Read only

A boolean value that returns true if the utterance queue contains as-yet-unspoken utterances.

SpeechSynthesis.speaking Read only

A boolean value that returns true if an utterance is currently in the process of being spoken — even if SpeechSynthesis is in a paused state.

SpeechSynthesis also inherits methods from its parent interface, EventTarget.

SpeechSynthesis.cancel()

Removes all utterances from the utterance queue.

SpeechSynthesis.getVoices()

Returns a list of SpeechSynthesisVoice objects representing all the available voices on the current device.

SpeechSynthesis.pause()

Puts the SpeechSynthesis object into a paused state.

SpeechSynthesis.resume()

Puts the SpeechSynthesis object into a non-paused state: resumes it if it was already paused.

SpeechSynthesis.speak()

Adds an utterance to the utterance queue; it will be spoken when any other utterances queued before it have been spoken.

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

voiceschanged

Fired when the list of SpeechSynthesisVoice objects that would be returned by the SpeechSynthesis.getVoices() method has changed. Also available via the onvoiceschanged property.

First, a simple example:

let utterance = new SpeechSynthesisUtterance("Hello world!");
speechSynthesis.speak(utterance);

Now we'll look at a more fully-fledged example. In our 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(), create a new SpeechSynthesisUtterance 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(".txt");
const voiceSelect = document.querySelector("select");
const pitch = document.querySelector("#pitch");
const pitchValue = document.querySelector(".pitch-value");
const rate = document.querySelector("#rate");
const rateValue = document.querySelector(".rate-value");

let voices = [];

function populateVoiceList() {
  voices = synth.getVoices();

  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";
    }

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

populateVoiceList();
if (speechSynthesis.onvoiceschanged !== undefined) {
  speechSynthesis.onvoiceschanged = populateVoiceList;
}

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

  const utterThis = new SpeechSynthesisUtterance(inputTxt.value);
  const selectedOption =
    voiceSelect.selectedOptions[0].getAttribute("data-name");
  for (let i = 0; i < voices.length; i++) {
    if (voices[i].name === selectedOption) {
      utterThis.voice = voices[i];
    }
  }
  utterThis.pitch = pitch.value;
  utterThis.rate = rate.value;
  synth.speak(utterThis);

  inputTxt.blur();
};

• Web Speech API