how to use ldr in Arduino

How to use LDR with relay module in Arduino :

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Code :

void setup() {

  pinMode(4,INPUT);

  pinMode(3,OUTPUT);

  digitalWrite(4,HIGH);

  

  // put your setup code here, to run once:

}

void loop() {

   

   if (digitalRead(4) == HIGH){

    digitalWrite(3,LOW);

   }

                     

   else{

    digitalWrite(3,HIGH);

   

  }}

  // put your main code here, to run repeatedly: