Select option 1 show option 2

Hello everyone, I am using ionic 2 + firebase 3, I would like to make one function : when user select a Date, it will show the corresponding timeslots for users to select.

Data Structure in firebase :
Date 1 - TimeSlot 1, TimeSlot 2, TimeSlot 3
Date 2 - TimeSlot 1, TimeSlot 2, TimeSlot 3, TimsSlot4
Date 3 - TimeSlot 1, TimeSlot 2, TimeSlot 3

I can get the data from firebase like below :

`<div *ngFor=“let timeSlot of timeSlotList” >


What I am thinking as below, I can get the value of selected date, but I don’t know how to use the selected date to show the corresponding timeslots and let users select. Could anyone give a help? Many thanks.

<ion-item> <ion-label>Select Booking Date</ion-label> <ion-select [(ngModel)]="slotId" (ionChange)="slotSelected($event, slotId)"> <ion-option *ngFor="let timeSlot of timeSlotList"> {{timeSlot?.date}} </ion-option> </ion-select> </ion-item>

slotSelected(slotId){ console.log("Booking Date", slotId); }