code: function validHex(t) {
  	for (var i = 0; i < t.length; i++) {
  		var c = t.charAt(i);
  		if (!((c >= 'a' && c <= 'f') || (c >= '0' && c <= '9'))) return false;
  	}
  	return true;
  }
docs: does this string consist of only hexadecimal digits?