04_make_it_better.js

04_make_it_better.js

// taken from http://www.dreamincode.net/code/snippet154.htm
//
// Find the weaknesses, and clean up the code.
// Find at least 3 things you can make better!
//
// Test numbers (return true):
// 4111111111111111
// 378282246310005
// 5555555555554444

function isCreditCard( CC ) {
     if (CC.length > 19)
          return (false);

     var sum = 0, mul = 1, l = CC.length;
     for (i = 0; i < l; i++)
     {
          digit = CC.substring(l-i-1,l-i);
          tproduct = parseInt(digit ,10)*mul;
          sum += tproduct >= 10 ? (tproduct % 10) + 1 : tproduct;
          mul = mul == 1 ? mul + 1 : mul - 1;
     }
    return (sum % 10) == 0;
}