Google Cloud Message：使用JavaScript从Cordova混合应用程序获取RegistrationId

I've just started to develop apps for android. I've done an Hybrid Cordova app in telerik platform, so I'm using javascript as language. I need to get push notification sent from a server to my android device. I have a project in Firebase and I set thecorrect google API Key and ProjectId in my code. In order to send the message from the server, I need the Registration ID of my app. How could I get? I found a lot of examples in Java, but none in javascript. Thanks!I've just started to develop apps for android.