speechRecognition.js

<script>
  speechRecognition = new webkitSpeechRecognition();
  speechRecognition.continuous = true;
  speechRecognition.lang = 'pt-br';
  speechRecognition.interimResults = true;
  speechRecognition.start();
  speechRecognition.onresult = function (event) {

    if (typeof (event.results) == 'undefined') {
      speechRecognition.stop();
      return;
    }
    for (var i = event.resultIndex; i < event.results.length; ++i) {
      if (event.results[i].isFinal) {
        let speech_text = event.results[i][0].transcript
        alert(speech_text);
      }
    }
  };
</script>