完整的JavaScript版的信用卡校验代码详解编程语言

function isValidCreditCard(type, ccnum) { 
   if (type == "Visa") { 
      // Visa: length 16, prefix 4, dashes optional. 
      var re = /^4/d{3}-?/d{4}-?/d{4}-?/d{4}$/; 
   } else if (type == "MC") { 
      // Mastercard: length 16, prefix 51-55, dashes optional. 
      var re = /^5[1-5]/d{2}-?/d{4}-?/d{4}-?/d{4}$/; 
   } else if (type == "Disc") { 
      // Discover: length 16, prefix 6011, dashes optional. 
      var re = /^6011-?/d{4}-?/d{4}-?/d{4}$/; 
   } else if (type == "AmEx") { 
      // American Express: length 15, prefix 34 or 37. 
      var re = /^3[4,7]/d{13}$/; 
   } else if (type == "Diners") { 
      // Diners: length 14, prefix 30, 36, or 38. 
      var re = /^3[0,6,8]/d{12}$/; 
   } 
   if (!re.test(ccnum)) return false; 
   // Remove all dashes for the checksum checks to eliminate negative numbers 
   ccnum = ccnum.split("-").join(""); 
   // Checksum ("Mod 10") 
   // Add even digits in even length strings or odd digits in odd length strings. 
   var checksum = 0; 
   for (var i=(2-(ccnum.length % 2)); i<=ccnum.length; i+=2) { 
      checksum += parseInt(ccnum.charAt(i-1)); 
   } 
   // Analyze odd digits in even length strings or even digits in odd length strings. 
   for (var i=(ccnum.length % 2) + 1; i<ccnum.length; i+=2) { 
      var digit = parseInt(ccnum.charAt(i-1)) * 2; 
      if (digit < 10) { checksum += digit; } else { checksum += (digit-9); } 
   } 
   if ((checksum % 10) == 0) return true; else return false; 
}