让元素隐藏或显示, 最好是在css中设置一个类, 通过js控制类的变化来改变元素的状态.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            padding: 0;
            margin: 0;
        }
        div {
            width: 200px;
            height: 200px;
            background-color: pink;
        }
        .hide {
            display: none;
        }
        .show {
            display: block;
        }
    </style>
</head>
<body>
    <input type="button" value="点击隐藏" id="btn">
    <div id="box"></div>

    <script>
        var btn = document.getElementById("btn");
        var box = document.getElementById("box");

        btn.onclick = function(){
            //如果元素div当前是显示的, 就让他隐藏
            if(btn.value == "点击隐藏"){
                box.className = "hide";
                btn.value = "点击显示";
            }
            else {
                box.className = "show";
                btn.value = "点击隐藏";
            }
            
        };

    </script>
</body>
</html>