//FCMPlugin.getToken( successCallback(token), errorCallback(err) );
//Keep in mind the function will return null if the token has not been established yet.
FCMPlugin.getToken(
  function(token){
    alert(token);
  },
  function(err){
    console.log('error retrieving token: ' + err);
  }
)

//FCMPlugin.subscribeToTopic( topic, successCallback(msg), errorCallback(err) );
//All devices are subscribed automatically to 'all' and 'ios' or 'android' topic respectively.
//Must match the following regular expression: "[a-zA-Z0-9-_.~%]{1,900}".
FCMPlugin.subscribeToTopic('topicExample');

//FCMPlugin.unsubscribeFromTopic( topic, successCallback(msg), errorCallback(err) );
FCMPlugin.unsubscribeFromTopic('topicExample');

//FCMPlugin.onNotification( onNotificationCallback(data), successCallback(msg), errorCallback(err) )
//Here you define your application behaviour based on the notification data.
FCMPlugin.onNotification(
  function(data){
    if(data.wasTapped){
      //Notification was received on device tray and tapped by the user.
      alert( JSON.stringify(data) );
    }else{
      //Notification was received in foreground. Maybe the user needs to be notified.
      alert( JSON.stringify(data) );
    }
  },
  function(msg){
    console.log('onNotification callback successfully registered: ' + msg);
  },
  function(err){
    console.log('Error registering onNotification callback: ' + err);
  }
);

//POST: https://fcm.googleapis.com/fcm/send
//HEADER: Content-Type: application/json
//HEADER: Authorization: key=AIzaSy*******************
{
  "notification":{
    "title":"Notification title",  //Any value
    "body":"Notification body",  //Any value
    "sound":"default", //If you want notification sound
    "click_action":"FCM_PLUGIN_ACTIVITY",  //Must be present for Android
    "icon":"fcm_push_icon"  //White icon Android resource
  },
  "data":{
    "param1":"value1",  //Any data to be retrieved in the notification callback
    "param2":"value2"
  },
    "to":"/topics/topicExample", //Topic or single device
    "priority":"high", //If not set, notification won't be delivered on completely closed iOS app
    "restricted_package_name":"" //Optional. Set for application filtering
}