// This takes time... keep the voice reference somewhere before clicking on something
let voice_type = speechSynthesis.getVoices().find(function(voice) { return voice.name == 'Samantha'; });

// e.g. after click event
var msg = new SpeechSynthesisUtterance();
msg.voice = voice_type;
msg.text = "Awesome!";
msg.rate = 1.4;
msg.pitch = 3.0;
window.speechSynthesis.speak(msg);