Trouble in fetching firebase data

ionViewDidEnter(){
      this.firebaseData.getBillDetail(this.navParams.get('billId'))
      .on('value', snapshot => {
        this.currentBill = snapshot.val();
        this.currentBill.id = snapshot.key;
      });

    }

How can I refere each child... Can anyone suggest forEach function to capture the child IDs created.. Further those ids can be looped to get items contained in these IDs