JS elementSibling

window.onload=function(){
    document.getElementById('btn').addEventListener('click', function(){
        let d1=document.getElementById('item1');
        let d2=d1.nextElementSibling;  //다음값 
        console.log(d1);
        console.log(d2);
 
        let d3=d2.previousElementSibling; //이전값
        console.log(d3);
 
        let d4=d2.nextElementSibling;
        console.log(d4);
    });
}