JS realizes the effect of Baidu News navigation bar

<div class="box">
        <!--Two red background blocks-->
        <!--Background block that moves with the mouse-->
        <div id="move"></div>
        <!--The background block fixed somewhere after the mouse clicks-->
        <div id="fixed"></div>
        <a href="#">Home</a>
        <a href="#">Domestic</a>
        <a href="#">International</a>
        Military
        <a href="#">Finance</a>
        <a href="#">Entertainment</a>
        <a href="#">Sports</a>
        <a href="#">Internet</a>
        <a href="#">Technology</a>
        <a href="#">Games</a>
        <a href="#">Woman</a>
        <a href="#">Car</a>
        <a href="#">Property</a>
</div>

 *{
            margin: 0;
            padding: 0;
        }
        .box{
            top:100px;
            width: 790px;
            height: 30px;
            font-size: 0;
            position: relative;
            margin: 0 auto;
            background-color: #01204f;
        }
        a{
            display: inline-block;
            position: relative;
            width: 60px;
            height: 30px;
            line-height: 30px;
            color: white;
            font-size: 16px;
            text-decoration: none;
            text-align: center;
            transition: all 0.6s;
        }
        #move{
            position: absolute;
            background-color: red;
            top: 0px;
            left: 0px;
            width: 60px;
            height: 30px;
            transition: all 0.6s;
        }
        #fixed{
            position: absolute;
            background-color: red;
            top: 0px;
            left: 0px;
            width: 60px;
            height: 30px;
        }

window.onload = function () {
      let move = document.getElementById("move");//Sliding background block let fixed = document.getElementById("fixed");//Background block fixed somewhere let aList = document.getElementsByTagName("a");//a tag list let left = move.offsetLeft + "px";//Initial position of sliding background block //Bind all a tags to move in, move out, and click events for (let i = 0; i < aList.length; i++) {
                aList[i].onmouseover = function () {
                    // When the mouse moves into a certain a tag, the sliding background block slides to the position of the current a tag move.style.left = aList[i].offsetLeft + "px";
                }
                aList[i].onmouseout = function () {
                    // When the mouse moves out of label a, the sliding background block returns to the initial position move.style.left = left;
                }
                aList[i].onclick = function () {
                    // After a certain a tag is clicked, the fixed background block moves to the position of the current a tag fixed.style.left = aList[i].offsetLeft + "px";
                    // Update the initial position of the sliding background block to the current position of label a left = aList[i].offsetLeft + "px";
                }
            }
        }