How to activate Google Web Speech API recognition with a passphrase?

Question

Google

I use Google Web Speech API in my project. But the fact is that you need to press a button to start recognition. Or Google is constantly listening to the air, which is not very good. Yes, and traffic eats.
How to implement listening to the broadcast online? To set one voice phrase - like OK GOOGLE.
How is it implemented on the main page of Google? There, if you say OK Google, then he somehow listens to you. And then asks about turning on the microphone. You just need to implement something like this.
There is an option to install pocketsphinx.js. and set up there - but this, as I understand it, is a crutch.

Answer 1

In general, I came up with Crutches) but they work fine for that, though they only recognize English. But it doesn't matter, you can come up with any word for activation.
https://github.com/TalAter/annyang