How can I reverse data array of Firestore ? Angular 6

Question

listItemAds() {
        this.itemList = this.afs.collection<Class>('Collection');

        this.itemList.snapshotChanges().subscribe(list => {
        this.itemArray = [];
        list.forEach(action => {
        const data = action.payload.doc.data() as Class;
        this.itemArray.push(data);
-->  this.itemArray.reverse(); // I try use this.itemArray.reverse(data.idNumber) ==> error
           });
         });
         console.log(this.itemArray);

      }

I wanna reverse data from New data to Old data , I set idNumber in object ex:[1,2,3,4,5].

Note

Answer 1

You can use the orderBy query option in your collection call.

The Firebase documentation on ordering & limiting shows you how to use orderBy specifically.

Using the server to sort data results in better client performance.

this.itemList = this.afs.collection<Class>(
    'Collection',
    ref => ref.orderBy('idNumber', 'desc')
);
this.itemList.subscribe(list => {
    console.log(list);
});