Debounce Input (Button)

//WITH RESISTOR ,
//pinMode(buttonPin, INPUT);
//digitalWrite(buttonPin, HIGH); //CLOSE
//digitalWrite(buttonPin, LOW); //OPEN
//
//WITHOUT RESISTOR
//pinMode(buttonPin, INPUT_PULLUP);
//digitalWrite(buttonPin, LOW); //CLOSE
//digitalWrite(buttonPin, HIGH); //OPEN



#define buttonPinRes 3
int buttonStateRes;
int lastButtonStateRes = LOW;
unsigned long lastDebounceTimeRes = 0;
unsigned long debounceDelay = 50;
bool resSelected = false;

void setup()
{
 Serial.begin(9600);
  pinMode(buttonPinRes, INPUT_PULLUP);

}

void loop() {
readBtnRes();
 booleanCheck();
}

void readBtnRes() {
    int reading = digitalRead(buttonPinRes);
  if (reading != lastButtonStateRes) {
    lastDebounceTimeRes = millis();
  }
  if ((millis() - lastDebounceTimeRes) > debounceDelay) {
    if (reading != buttonStateRes) {
      buttonStateRes = reading;
      if (buttonStateRes == LOW) {
        resSelected = true;
      }
    }
  }
  lastButtonStateRes = reading;
}

void booleanCheck()
{
  if(resSelected)
  {
    Serial.print("TRUE");
  }
}