jQuery 셔틀 효과 구현

<div id="box">
  <div id="boxleft">
   <ul id="left_ul">

   </ul>
  </div>
  <div id="boxbtn">
   <button id="btn_right">>>>></button>
   <button id="btn_left">
    <<<< </button>
  </div>
  <div id="boxright">
   <ul id="right_ul">

   </ul>
  </div>
</div>

<style>
  * {
   margin: 0 auto;
   padding: 0;
   list-style: none;
  }

  #box {
   width: 500px;
   display: flex;
   justify-content: space-around;
   margin-top: 20px;
  }

  #boxright {
   width: 200px;
   height: 500px;
   border: 1px solid darkcyan;
  }

  #boxleft {
   width: 200px;
   height: 500px;
   border: 1px solid darkcyan;
  }

  #boxbtn {
   margin: auto;
  }

  #boxbtn button {
   width: 50px;
   height: 200ox;
   margin-top: 10px;
   display: flex;
   background: deepskyblue;
   cursor: pointer;
   color: white;
  }

  ul li {
   height: 30px;
   line-height: 30px;
   margin-bottom: 2px;
   text-align: center;
   background: darkgray;
  }

  form {
   text-align: center;
  }

  .active {
   color: white;
   background: darkseagreen;
  }
</style>

<script>
  let arr = [
   { "id": 1, "name": "zhang", "check": false },
   { "id": 2, "name": "liu", "check": false },
   { "id": 3, "name": "guan", "check": false },
   { "id": 4, "name": "zhao", "check": true },
   { "id": 5, "name": "ao", "check": true }
  ];

  $("#add").click(function () {
   var name = $("#name").val();
   arr.push({ "name": name });
   showUL(arr);
  })
  $(function () {
   showUL(arr);
  })
  function showUL(arr) {
   var leftstr = "";
   var rightstr = "";
   for(let i in arr) {
    let { id, name, check } = arr[i];
    if (check) {
     rightstr += `
      <li _id="${id}">${name}</li>
    `
    } else {
     leftstr += `
      <li _id="${id}">${name}</li>
    `
    }

   }
   $("#left_ul").html(leftstr);
   $("#right_ul").html(rightstr);
  }


  $("#left_ul").on("click", "li", function () {
   let index = arr.findIndex((v) => {
    return v.id == $(this).attr("_id");
   })

   if ($(this).hasClass('active')) {
    $(this).removeClass('active');
    arr[index].check = false;
   } else {
    $(this).addClass('active');
    arr[index].check = true;
   }
  });
  $("#right_ul").on("click", "li", function () {
   let index = arr.findIndex((v) => {
    return v.id == $(this).attr("_id");
   })

   if ($(this).hasClass('active')) {
    $(this).removeClass('active');
    arr[index].check = true;
   } else {
    $(this).addClass('active');
    arr[index].check = false;
   }
  });
  $("#btn_right").click(function () {
   if ($("#left_ul .active").length == 0) return false;

   showUL(arr);
  })
  $("#btn_left").click(function () {
   if ($("#right_ul .active").length == 0) return false;
  
   showUL(arr);
  })  
</script>