byte ledpins[] = {2,3,4,5,6,7,8,9};

int val;

void setup() {
 for (byte i = 0; i < 8; i++){
      pinMode(ledpins[i], OUTPUT);
  }
}

void loop(){
val = analogRead(0);
val = map(val, 0, 1023, 0, 8);

for (byte i = 0; i < val; i++){
    digitalWrite(ledpins[i], HIGH);
}
for (byte i = 0; i < 8; i++){
    digitalWrite(ledpins[i], LOW);
}
}