how to do text to speech in javascript

var msg = new SpeechSynthesisUtterance();
msg.text = "Hello World";
window.speechSynthesis.speak(msg);

$('#start-record-btn').on('click', function(e) {
  recognition.start();
});

function readOutLoud(message) {
  var speech = new SpeechSynthesisUtterance();

  // Set the text and voice attributes.
  speech.text = message;
  speech.volume = 1;
  speech.rate = 1;
  speech.pitch = 1;

  window.speechSynthesis.speak(speech);
}

var mobileRepeatBug = (current == 1 && transcript == event.results[0][0].transcript);

if(!mobileRepeatBug) {
  noteContent += transcript;
  noteTextarea.val(noteContent);
}

recognition.onresult = function(event) {

  // event is a SpeechRecognitionEvent object.
  // It holds all the lines we have captured so far. 
  // We only need the current one.
  var current = event.resultIndex;

  // Get a transcript of what was said.
  var transcript = event.results[current][0].transcript;

  // Add the current transcript to the contents of our Note.
  noteContent += transcript;
  noteTextarea.val(noteContent);
}

$('#pause-record-btn').on('click', function(e) {
  recognition.stop();
});