isEmailOrTel function

String? isEmailOrTel(
  1. String? val
)

return an error message if value does not pass the validation validation requires val: not equal null, must contain @ char, must contain dot(".") and length must be more than 4 characters

Implementation

String? isEmailOrTel(String? val) {
  final RegExp reg = RegExp(
      r"^([a-zA-Z\d\.-]+)@([a-z\d-]+)\.([a-z]{2,8})(\.[a-z]{2,8})?$|^\+[0-9]{8,17}$");

  return reg.hasMatch(val ?? "")
      ? null
      : "enter a valid email or telephone number";
}