Is it possible to implement hotword detection in Ionic app

I am trying to build an app using Angular 7 and Ionic 4 to facilitate examinations for blind folks. So far, I have integrated my app with API.ai and Ionic Speech Recognition and TTS, but the problem is speech recognition works on a click of a button. Is it possible to implement always listening kind of a solution just like Google Assistant. I am planning to develop fully interactive app capable of reading out question and recording answers. How can I enable mic using voice commands?