ios – How to know if the first item in the list that is inside of a ForEach loop is visible in SwiftUI?

You can use enumerated() along with ForEach to track an index of the array and use it to hide and show your button. Something like this.

struct ContentView: View {
    
    let items = (1...50).map(String.init)
    @State private var showScrollButton = false
   
    var body: some View {
        ScrollViewReader { reader in
            ZStack(alignment: .bottomTrailing) {
                List {
                    let enumerated = items.enumerated().map({ $0 })
                    ForEach(enumerated, id: \.element) { (index, item) in
                        Text(item)
                            .id(index)
                            .onAppear {
                                guard index == 0, showScrollButton else {
                                    return
                                }
                                showScrollButton = false
                            }
                            .onDisappear {
                                guard index == 0, !showScrollButton else {
                                    return
                                }
                                showScrollButton = true
                            }
                    }
                }
                if showScrollButton {
                    Button(action: {
                        withAnimation {
                            reader.scrollTo(0, anchor: .top)
                        }
                    }, label: {
                        Image(systemName: "chevron.up.circle")
                            .font(.largeTitle)
                            .foregroundColor(.black)
                            .padding()
                            .padding(.trailing)
                    })
                }
            }
        }
    }
}