Native javascript+CSS to achieve the effect of carousel

<ul id="banner" ></ul>

ul{
    list-style:none;
    position: absolute;
    padding: 0;
    left: 0;
    right: 0;
    bottom: 0;
    top:0;
    margin:auto;
    width: 800px;
    height:200px;
}

//Generate a carousel export function generateBanner(){
  let sz = new Array();
  let cur_ul = document.getElementById('banner');
  const recommends = this.recommends;

  let timer = setInterval(getNextLi, 3000);

  //Generate the carousel image li
  for (let i = 0; i < recommends.length; i++) {
    //Generate tags let cur_li = document.createElement("li");
    let cur_img = document.createElement("img");
    //Add attributes cur_img.src = recommends[i].pic;
    //Add style cur_li.style.position = 'absolute';
    cur_li.style.left = '0px';
    cur_li.style.transitionDuration = '0.4s';
    cur_li.style.cursor="pointer";

    //ul total width 800, showing one complete 400px and two incomplete 200px
    cur_img.style.width = '125px';
    cur_img.style.height = "100px";

    //Append child element cur_li.appendChild(cur_img);
    cur_ul.appendChild(cur_li);

    //Put all into array for easy operation sz.push(cur_li);
  }

  //Generate two icons generateAngleIcons();

  //Use the last three pictures to display let len ​​= sz.length - 1;
  //The third from the last showThreeLi();

  //Get the next li display and put the first one at the end of the array function getNextLi() {
    const li = sz[0];
    sz = sz.slice(1);
    sz.push(li);

    //All li are restored for (let i = 0; i < sz.length; i++) {
      //All li are restored to their original size sz[i].style.transform = "scale(1)";
      sz[i].style.left = "0px";
      //li covers from small to large sz[i].style.zIndex = i;

      //Hide all sz[i].style.display = "none";
    }
    //Show the last three pictures showThreeLi();

  }

  //Show the last three pictures function showThreeLi() {
    sz[len - 2].style.left = "0px";
    //The second to last picture sz[len - 1].style.left = "120px";
    sz[len - 1].style.zIndex = 100;
    sz[len - 1].style.transform = "scale(1.3)";
    //The last one sz[len].style.left = "230px";

    //Display sz[len - 2].style.display = "block";
    sz[len - 1].style.display = "block";
    sz[len].style.display = "block";
  }


  function generateAngleIcons(){
    const icons = new Array();

    for (let i = 0; i < 2; i++) {
      //Generate icon li
      let cur_li = document.createElement("li");
      //Add style cur_li.style.position = 'absolute';
      cur_li.style.top = '0px';
      cur_li.style.bottom = '0px';
      cur_li.style.margin = "auto";
      cur_li.style.paddingTop="100px";
      cur_li.style.paddingBottom="100px";
      cur_li.style.zIndex = 20;
      icons.push(cur_li);
    }

    icons[0].style.left = '0px';
    icons[1].style.right = '0px';
    icons[0].innerHTML = '<i class="angle left icon"></i>'
    icons[1].innerHTML = '<i class="angle right icon"></i>'
    cur_ul.appendChild(icons[1]);
    cur_ul.appendChild(icons[0]);
  }
}