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console 命令行工具 X clear

                    
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console
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        
        .outter {
            width: 800px;
            border: 2px solid black;
            overflow: hidden;
            margin: 0 auto;

        }
        
        .left {
            width: 20%;
            height: 500px;
            float: left;
            background-color: pink;
        }
        
        .right {
            width: 80%;
            height: 500px;
            float: left;
            background-color:lightyellow;
        }
        
        #bar {
            width: 30px;
            height: 50px;
            padding-left: 5px;
            background-color: green;
            border-bottom-right-radius: 15px;
        }
    </style>
</head>
<body>
   <div class="outter">
        <div class="left" id="left">
            <ol>
                <li>菜单1</li>
                <li>菜单2</li>
                <li>菜单3</li>
                <li>菜单4</li>
                <li>菜单5</li>
            </ol>
        </div>
        <div class="right" id="right">
            <div id="bar">收起</div>
        </div>
    </div>
    <script>
        var bar = document.getElementById("bar");
        var left = document.getElementById("left");
        var right = document.getElementById("right");
        bar.onclick = function (){
            if(!left.style.display.match("none")){
                left.style.display = "none"
                right.style.width = "100%"
                bar.innerHTML = "隐藏"
            }else{
                left.style.display = "block"
                right.style.width = "80%"
                bar.innerHTML = "收起"
            }
        }
    </script>
</body>
</html>