完整的JavaScript版的信用卡校验代码

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