I want to make my div not automatic scroll down when user scrolling up or not at bottom But i think make some mistake so my code doesn't work

code which always scroll down :

Js

setInterval(() =>{
let xhr = new XMLHttpRequest();
xhr.open("POST", "php/get-chat.php", true);
xhr.onload = ()=>{
  if(xhr.readyState === XMLHttpRequest.DONE){
      if(xhr.status === 200){
        let data = xhr.response;
        chatBox.innerHTML = data;
        if(!chatBox.classList.contains("active")){
            scrollToBottom();
          }
      }
  }
}
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhr.send("incoming_id="+incoming_id);
}, 500);

function scrollToBottom(){
chatBox.scrollTop = chatBox.scrollHeight;
}

Thanks for the answer