SpeechSynthesisUtterance
function speak (message) {
var msg = new SpeechSynthesisUtterance(message)
var voices = window.speechSynthesis.getVoices()
msg.voice = voices[0]
window.speechSynthesis.speak(msg)
}
speak('Hello, world')
See: SpeechSynthesisUtterance (developer.mozilla.org)