console 命令行工具 X clear
console
<!DOCTYPE html>
<html>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
    </style>
    <body>
        <div id="listBox">
            <div style="width: 60px; border: 1px solid black;">1</div>
            <div style="display: none;" id="listsBox">2</div>
        </div>
    </body>
</html>
<script>
    var listBox = document.querySelector('#listBox')
    var listsBox = document.querySelector('#listsBox')
    listBox.onmouseover = function () {
        listsBox.style="display: block; width: 60px; border: 1px solid black; "
    }
    listBox.onmouseout = function () {
        listsBox.style="display: none;"
    }
</script>