escape

# File activesupport/lib/active_support/json/encoding.rb, line 121
        def escape(string)
          if string.respond_to?(:force_encoding)
            string = string.encode(::Encoding::UTF_8, :undef => :replace).force_encoding(::Encoding::BINARY)
          end
          json = string.
            gsub(escape_regex) { |s| ESCAPED_CHARS[s] }.
            gsub(/([\xC0-\xDF][\x80-\xBF]|
                   [\xE0-\xEF][\x80-\xBF]{2}|
                   [\xF0-\xF7][\x80-\xBF]{3})+/x) { |s|
            s.unpack("U*").pack("n*").unpack("H*")[0].gsub(/.{4}/, '\\u\&')
          }
          json = %("#{json}")
          json.force_encoding(::Encoding::UTF_8) if json.respond_to?(:force_encoding)
          json
        end