জেকুয়েরী focus

<!DOCTYPE html>
<html>
<script src="https://code.jquery.com/jquery-3.7.1.min.js"></script>
<body>

<input placeholder="এখানে ক্লিক করুন">

<script>
$(document).ready(function(){
  $("input").focus(function(){
    $(this).css("background", "lightgreen");
  });

});
</script>
</body>
</html>