function isAlphaNumeric(c) {
  var charCode = c.charCodeAt(0);

  if (charCode < 47) {
    // #.
    return charCode === 35 || charCode === 46;
  }
  if (charCode < 59) {
    // 0-9 and :
    return charCode > 47;
  }
  if (charCode < 91) {
    // A-Z
    return charCode > 64;
  }
  if (charCode < 96) {
    // _
    return charCode === 95;
  }
  if (charCode < 123) {
    // a-z
    return charCode > 96;
  }

  return false;
}
Test whether given character is alphabetic or numeric ( a-zA-Z_0-9.:# )
@param {string} c
@returns {boolean} isAlphaNumeric