check static method

String check(
  1. String twelve
)

Modulo-10 check digit for the first 12 digits.

Implementation

static String check(String twelve) {
  var sum = 0;
  for (int i = 0; i < 12; i++) {
    final int d = twelve.codeUnitAt(i) - 0x30;
    sum += d * (i.isEven ? 1 : 3);
  }
  return '${(10 - sum % 10) % 10}';
}