js单例模式--实现点击只有一个弹窗

 1 <head>
 2     <meta charset="UTF-8">
 3     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 4     <title>Document</title>
 5     <style>
 6         .model {
 7              200px;
 8             height: 200px;
 9             border: 1px solid aqua;
10             position: fixed;
11             top: 50%;
12             left: 50%;
13             transform: translate(-50%, -50%);
14             text-align: center;
15         }
16     </style>
17 </head>
18 
19 <body>
20     <div id="loginBtn">点我</div>
21     <script>
22         var getSingle = function (fn) {
23             var result; //缓存实例
24             return function () {
25                 return result || (result = fn.apply(this, arguments))
26             }
27         }
28         var createLoginLayer = function () {
29             var oDiv = document.createElement("div");
30             oDiv.innerHTML = "我是登录浮窗";
31             oDiv.className = "model";
32             oDiv.style.display = "none";
33             document.body.appendChild(oDiv);
34             return oDiv;
35         }
36         var createSingleLoginLayer = getSingle(createLoginLayer);
37         document.getElementById("loginBtn").onclick = function () {
38             //动态创建弹窗
39             //新建一个弹窗实例，内部使用单例模式管理，一直只能有一个.
40             var loginLayer = createSingleLoginLayer();
41             loginLayer.style.display = "block"
42         }
43     </script>
44 </body>