In ionic, how to send array selected items to firebase DB

Question

I have developed simple shopping cart. i am getting and displayed selected items successfully in html but need to store selected items (created as array) to firebase Database. I don't know how can I write selected items to firebase, if anyone knows kindly help me out.

 

this is my array created at cart.service.ts

 

 

cart.page.html

<form [formGroup]="createDataForm" (submit)="createData()">
<ion-list>

 <ion-grid><ion-row *ngFor="let item of selectedItems" lines="inset">
  <ion-col size="5"><div>{{ item.name }} - {{ item.price | currency:'USD':'symbol' }}</div></ion-col>
  <ion-col size="4.5">

  <ion-col size="2"><ion-label text-right> {{ (item.price * item.count) | currency:'USD':'symbol' }}
   </ion-label></ion-col>
   </ion-row></ion-grid>
  </ion-list>