如果先创建，等需要的时候弹出是浪费资源的。
如果等点登录按钮创建，关闭再删除，再点击创建，关闭删除，非常耗费内存。
这样就可以用到前面的单例模式，进行判断，如果没有就创建，有了就直接用。
按需创建的单例模式
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| <!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>
body {
background-color: #f0f0f0;
}
#loginLayer {
position: absolute;
left: 240px;
top: 80px;
200px;
height: 200px;
border: 1px solid #ccc;
background-color: #fff;
text-align: center;
}
#maskLayer {
position: absolute;
left: 0;
top: 0;
100%;
height: 100%;
background-color: #000;
opacity: 0.3;
}
</style>
</head>
<body>
<button id="loginBtn">登录</button>
<!-- <div id="loginLayer">登录窗口</div>
<div id="maskLayer"></div> -->
<script>
var createLoginLayer = (function () {
var loginLayer =null;
return function () {
大专栏 登录框-使用惰性生成 if (!loginLayer) {
loginLayer = document.createElement("div");
loginLayer.id = "loginLayer";
loginLayer.innerHTML = "登录窗口";
loginLayer.style.display = "none";
document.body.appendChild(loginLayer);
}
return loginLayer;
};
})();
var createMaskLayer = (function () {
var maskLayer =null;
return function () {
if (!maskLayer) {
maskLayer = document.createElement("div");
maskLayer.id = "maskLayer";
maskLayer.innerHTML = "登录窗口";
maskLayer.style.display = "none";
document.body.appendChild(maskLayer);
}
return maskLayer;
};
})();
document.getElementById("loginBtn").onclick = function () {
var maskLayer = createMaskLayer();
var loginLayer = createLoginLayer();
loginLayer.style.display = "block";
maskLayer.style.display = "block";
};
</script>
</body>
</html>
|
修改为通用单例模式
职责分开：节点创建，创建单例
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|
function createLoginLayer() {
loginLayer = document.createElement("div");
loginLayer.id = "loginLayer";
loginLayer.innerHTML = "登录窗口";
loginLayer.style.display = "none";
document.body.appendChild(loginLayer);
return loginLayer;
}
function createMaskLayer() {
maskLayer = document.createElement("div");
maskLayer.id = "maskLayer";
maskLayer.innerHTML = "登录窗口";
maskLayer.style.display = "none";
document.body.appendChild(maskLayer);
return maskLayer;
}
function getSingleton(fn) {
var instance = null;
return function () {
return instance || (instance = fn())//instance = fn.apply(null,arguments)
};
}
var createSingletonLoginLayer = getSingleton(createLoginLayer);
var createSingletonMaskLayer = getSingleton(createMaskLayer);
document.getElementById("loginBtn").onclick = function () {
var maskLayer = createSingletonMaskLayer();
var loginLayer = createSingletonLoginLayer();
loginLayer.style.display = "block";
maskLayer.style.display = "block";
};
|