https://simple-clear.com/js/speech.js

1var synth = window.speechSynthesis;
2
3window.speak = function (text, objRef) {
4    if (synth.speaking) {
5        console.error('speechSynthesis.speaking');
6        return;
7    }
8    if (text !== '') {
9        var utterThis = new SpeechSynthesisUtterance(text);
10        utterThis.onend = function (event) {
11            console.log('SpeechSynthesisUtterance.onend');
12            objRef.invokeMethodAsync('OnEnd');
13        }
14        utterThis.onerror = function (event) {
15            console.error('SpeechSynthesisUtterance.onerror');
16        }
17        //var selectedOption = voiceSelect.selectedOptions[0].getAttribute('data-name');
18
19        voices = synth.getVoices();
20        for (i = 0; i < voices.length; i++) {
21            if (voices[i].lang === "en-GB") {
22                utterThis.voice = voices[i];
23                break;
24            }
25        }
26
27        if (utterThis.voice !== "en-GB") {
28            for (i = 0; i < voices.length; i++) {
29                if (voices[i].lang.startsWith("en")) {
30                    utterThis.voice = voices[i];
31                    break;
32                }
33            }
34        }
35
36        //utterThis.voice = voices[5];
37        utterThis.pitch = 1;
38        utterThis.rate = 1;
39        synth.speak(utterThis);
40    }
41}
42
43function populateVoiceList() {
44    voices = synth.getVoices().sort(function (a, b) {
45        const aname = a.name.toUpperCase(), bname = b.name.toUpperCase();
46        if (aname < bname) return -1;
47        else if (aname == bname) return 0;
48        else return +1;
49    });
50    var selectedIndex = voiceSelect.selectedIndex < 0 ? 0 : voiceSelect.selectedIndex;
51    voiceSelect.innerHTML = '';
52    for (i = 0; i < voices.length; i++) {
53        var option = document.createElement('option');
54        option.textContent = voices[i].name + ' (' + voices[i].lang + ')';
55
56        if (voices[i].default) {
57            option.textContent += ' -- DEFAULT';
58        }
59
60        option.setAttribute('data-lang', voices[i].lang);
61        option.setAttribute('data-name', voices[i].name);
62        voiceSelect.appendChild(option);
63    }
64    voiceSelect.selectedIndex = selectedIndex;
65}