Credit_card_issuer.rb

puts "Enter Credit card Number"
input = gets.to_s
if input =~ /[a-zA-Z[<>%\$~``!@#^&*()+=?;:{}\|''""'"]]/        # REGEX to validate Card Number
    puts "Invalid Number"
else
    val = input.gsub!(/[\D\s+]/, '')                            # val is the variable, storing the Card Number
  
      if val =~ /^4/ and val.length >= 12 and val.length <= 19
          puts "Visa"
      elsif val =~ /^(5|2)[1-7][0-9]/ and val.length.eql?(16)
          puts "Mastercard"
      elsif val =~ /^6[0|2|4|5][14[0-9][0-9]]/ and val.length.eql?(16)
          puts "Discover"
      elsif val =~ /^3[4|7][0-9]/ and val.length.eql?(15)
          puts "American Express"  
      elsif val =~ /^3[5][0-9][0-9]/ and val.length >= 16 and val.length <= 19
          puts "JCB (Japan Credit Bureau)" 
      elsif val =~ /^(5|6)[0-9][0-9]/ and val.length >= 12 and val.length <= 19
          puts "Maestro" 
      elsif val =~ /^3[0|6|8][0-9][0-9]/ and val.length.eql?(14)
           puts "Diners Club Carte Blanche"  
      elsif val =~ /^3[0|9|8][0-9][0-9]/ and val.length.eql?(16)
          puts "Diners Club International"
      elsif val =~ /^2[0|1][1|4][4|9][0-9]/ and val.length.eql?(15)
          puts "enRoute"
      else
        puts "The Card issuer is out of our coverage"
      end  
    end