ESCAPE_MAP   =   { '"' => '\\"', "'" => "\\'" }

def escape_quotes(str)
  if str
    result = str.gsub(/(\|<\/|\r\n|\342\200\250|\342\200\251|[\n\r"'])/u) {|match| ESCAPE_MAP[match] }
  else
    ''
  end
end


string = 'double-quotes "escaped"'
escapedStr = escape_quotes(string)

puts escapedStr
=> double-quotes \"escaped\"