isNumber method

bool isNumber(
  1. String _s
)

QUEST: sure you can do better? is it number?

Implementation

bool isNumber(String _s) {
  bool retB = false;
  //  using #contains, instead of if   ('0123456789'.indexOf(_s) > -1)
  if ('0123456789'.contains(_s)) {
    retB = true;
    //  print('------------yep, is number');
  }
  return retB;
}