Changing System Alert

I have following code to remove few items. This generates system alert and I am not sure how to modify it

removeNewItem(itemName: string ){
  return firebase.database().ref('/Items' ).remove((error) => {    
    alert(error ? "Problem in removing items" : "Items Removed from List")
  }); 
}

Pls suggest

Sorry for this post… Its sorted with simple if, then and alertCtrl