SpeechSynthesis API onend callback not working

While this is how I found it to make it work, I am not sure if this is the right behavior....

First don't call the speak function it right away, use callback.

2nd, to get time use timeStamp instead of elapsedTime. You could have just used performance.now() as well.

var btn = document.getElementById('btn');
speechSynthesis.cancel()
var u = new SpeechSynthesisUtterance();
u.text = "This text was changed from the original demo.";

var t;
u.onstart = function (event) {
    t = event.timeStamp;
    console.log(t);
};

u.onend = function (event) {
    t = event.timeStamp - t;
    console.log(event.timeStamp);
    console.log((t / 1000) + " seconds");
};

btn.onclick = function () {speechSynthesis.speak(u);};

Demo: http://jsfiddle.net/QYw6b/2/

you get time passed and both events fired for sure.

According to this comment on the bug mentioned in the answer from Kevin Hakanson, it might be a problem with garbage collection. Storing the utterance in a variable before calling speak seems to do the trick:

window.utterances = [];
var utterance = new SpeechSynthesisUtterance( 'hello' );
utterances.push( utterance );
speechSynthesis.speak( utterance );