无效的正则表达式，无需重复任何操作即可验证信用卡号类型

Question

I've the following regular expression used for validating credit card number type using javascript

var match = /^(?:(4[0-9]{12}(?:[0-9]{3})?)|(5[1-5][0-9]{14})|?(6(?:011|5[0-9]{2})[0-9]{12})|(3[47][0-9]{13})|(3(?:0[0-5]|[68][0-9])?[0-9]{11})|((?:2131|1800|35[0-9]{3})[0-9]{11}))$/.exec(cardno);

Previously this code was running perfectly but now it shows the above error. Can anyone check it out and make any changes?

Answer 1

A better method would be using the LUHN test. https://en.wikipedia.org/wiki/Luhn_algorithm

/*
mod10( cardNumber )
   parameters:
      this function takes the text string card number and runs the Mod 10 formula on its respective digits.
   description:
      Mod 10 is the check digit formula for the supported cards these functions attempt to validate.
   returns:
      this function returns true if the number passes the check digit test.
      false otherwise.
*/
function mod10( cardNumber ) { // LUHN Formula for validation of credit card numbers.
   var ar = new Array( cardNumber.length );
   var i = 0,sum = 0;

   for( i = 0; i < cardNumber.length; ++i ) {
      ar[i] = parseInt(cardNumber.charAt(i));
   }
   for( i = ar.length -2; i >= 0; i-=2 ) { // you have to start from the right, and work back.
      ar[i] *= 2;                      // every second digit starting with the right most (check digit)
      if( ar[i] > 9 ) ar[i]-=9;          // will be doubled, and summed with the skipped digits.
   }                               // if the double digit is > 9, ADD those individual digits together 

   for( i = 0; i < ar.length; ++i ) {
      sum += ar[i];                   // if the sum is divisible by 10 mod10 succeeds
   }
   return (((sum%10)==0)?true:false);       
}

Answer 2

在http://www.regex101.com上输入它，它会告诉您该块中的问号： 14})|?(6(应该删除，因为问号意味着前面的标记是可选的，但是它前面带有不是令牌的or运算符，请注意，这与?:表示非捕获组不同。