Ruby: Remove Filtered Characters from a String

filterString.rb

def filterString
  originalString = "Hello this is dog"
  filter = "Hdgol"
  
  puts "the original string is " + originalString
  puts "filter: " + filter 
  
  splitString = originalString.split(//)
  splitFilter = filter.downcase.split(//)
  
  for i in splitFilter
    splitString.delete(i)
    splitString.delete(i.upcase)
  end
  
  puts splitString.join()
  
end

filterString