const int ledPin = 3; 

int ledState = LOW;  // ledState used to set the LED
unsigned long delay1 = 0;  // will store last time LED was updated

void setup() {
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT);
}

void loop() {
  if (millis() - delay1 >= 1000) {
    // save the last time you blinked the LED
    delay1 = millis();

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }

    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);
  }
}