How to change the value of a position of an array from a doc on Ionic 4?

Ionic Framework
1

Hi everyone, i’m trying to change the value of this:

ideasmodel

but just know how to add values, now i need to once click on the item-list.page on a position of the value i want to change (i need also pass on params the index) it goes to the item-detail.page and need to load it but don’t know how to obtain this value.

            this.afs.doc(`users/${this.user.getUID()}`).update({
                ideas: firestore.FieldValue.arrayUnion(this.idea)
            })

Thanks you so much anyway