Looks like this bug is closed, but I found THIS online:
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My question was: why does window.speechSynthesis.getVoices() return empty array, after page is loaded and onready function is triggered? As you can see if you click on the link, same function returns an array of available voices of Chrome by onclick triger?
It seems Chrome loads window.speechSynthesis after the page load!
The problem is not in ready event. If I remove the line var voice=... from ready function, for first click it shows empty list in console. But the second click works fine.
It seems window.speechSynthesis needs more time to load after first call. You need to call it twice! But also, you need to wait and let it load before second call on window.speechSynthesis. For example, following code shows two empty arrays in console if you run it for first time:
// First speechSynthesis call
var voices = window.speechSynthesis.getVoices();
console.log(voices);
// Second speechSynthesis call
voices = window.speechSynthesis.getVoices();
console.log(voices);