Dynamic variable values can utilize extension functionality.

It is mainly used to act like Kotlin's let extension function, making it convenient to check whether a dynamic value is null or to check its type.

extension MExt<T> on T {
  void let(void Function(T it) block) {
    if (this != null) {
      block(this);
    }
  }

  void letType<R>(void Function(R it) block) {
    if (this is R) {
      block(this as R);
    }
  }
}
void main(){
  dynamic j = 100;
  j.let((it) {
    print("print j");
  });
  j.letType<int>((it){
    print("j is int");
  });
}

The biggest problem now is that it works perfectly fine when running variables of other types, but a NoSuchMethodError will be reported when running the values of dynamic variables.

You can see more in :Dartpad demo