1. Understand the singleton mode
Definition of singleton mode: Ensure that a class has only one instance and provide a global access point to access it
Singleton mode The core: to ensure that there is only one instance and provide global access
2. Singleton mode in JavaScript
In js, we often use global variables as singleton mode. For example:
var a={};
Why a can be used as a global variable, because it meets the following two conditions:
1. Object a is unique
2. a is defined in the global scope, providing global access
Note: However, it is recommended to use namespaces in js to reduce the number of global variables
3. Lazy singleton
Lazy singleton: an object instance created only when needed
Purpose: There are two buttons on the page. When clicked, a response pop-up window needs to be displayed and Load the corresponding css file
Note: Some developers are used to writing in the page when it loads, and then setting the hidden state, which will waste DOM nodes
The following is the implementation code:
1. Main page
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>单例模式</title> <style type="text/css"> body{ background: #fffff2; } h3{ text-align: center; } </style> </head> <body> <h3 id="创建唯一的窗口">创建唯一的窗口</h3> <button type="button" id="btn1">创建p1</button> <button type="button" id="btn2">创建p2</button> </body> <script type="text/javascript"> /** * 管理单例 */ var getSingle=function(fn){ var result; return function(){ return result || (result=fn.apply(this,arguments)); } }; // 弹框关闭打开 function LayerAction(){ this.layer=null;//弹窗element if(typeof this.setLayer !== "function"){ // 设置弹窗 LayerAction.prototype.setLayer=function(layer){ if(!layer){ console.error("参数不完整,必须传入layer"); return; }else{ this.layer=layer; } }; // 显示弹窗 LayerAction.prototype.showLayer=function(){ this.layer.style.display="block"; }; // 关闭弹窗 LayerAction.prototype.closeLayer= function(){ this.layer.style.display="none"; } ; } } /** * p1弹窗 */ var p1={ p1Layer:null, layerAction: new LayerAction(), // 创建p1弹窗 createp1Layer:function(){ var p=document.createElement("p"); p.innerHTML="我是p1"; p.style.display='none'; p.id="p1"; document.body.appendChild(p); var closeBtn=document.createElement("span"); closeBtn.innerText="关闭"; closeBtn.id="closep1"; p.appendChild(closeBtn); return p; }, // 引入p1弹窗样式列表 createp1Style: function() { var styleElement = document.createElement('link'); styleElement.type = 'text/css'; styleElement.href = 'p1.css'; styleElement.rel = 'stylesheet'; document.getElementsByTagName('head')[0].appendChild(styleElement); console.log(document.getElementsByTagName('head')[0].innerHTML); return styleElement }, // 为关闭按钮绑定事件 bindActionForCloseLayer: function(){ var that=p1; document.getElementById("closep1").onclick=function(){ that.layerAction.closeLayer(); } }, // 调用弹窗1 startp1Layer: function(){ var createp1singleLayer=getSingle(this.createp1Layer); var createp1singleStyle=getSingle(this.createp1Style); var bindCloseEvent=getSingle(this.bindActionForCloseLayer); var that=this; document.getElementById("btn1").onclick=function(){ createp1singleStyle(); that.p1Layer=createp1singleLayer(); that.layerAction.setLayer(that.p1Layer); that.layerAction.showLayer(); bindCloseEvent(); } } }; p1.startp1Layer(); /** * p2弹窗 */ var p2={ p2Layer:null, layerAction: new LayerAction(), // 创建p2弹窗 createp2Layer: function(){ var p=document.createElement("p"); p.innerHTML="我是p2"; p.style.display='none'; p.id="p2"; document.body.appendChild(p); var closeBtn=document.createElement("span"); closeBtn.innerText="关闭"; closeBtn.id="closep2"; p.appendChild(closeBtn); return p; }, // 引入p2弹窗样式列表 createp2Style: function () { var styleElement = document.createElement('link'); styleElement.type = 'text/css'; styleElement.href = 'p2.css'; styleElement.rel = 'stylesheet'; document.getElementsByTagName('head')[0].appendChild(styleElement); console.log(document.getElementsByTagName('head')[0].innerHTML); return styleElement }, // 为关闭按钮绑定事件 bindActionForCloseLayer: function(){ var that=p2; document.getElementById("closep2").onclick=function(){ that.layerAction.closeLayer(); } }, // 调用弹窗2 startp2Layer: function(){ var createp2singleLayer=getSingle(this.createp2Layer); var createp2singleStyle=getSingle(this.createp2Style); var bindCloseEvent=getSingle(this.bindActionForCloseLayer); var that=this; document.getElementById("btn2").onclick=function(){ createp2singleStyle(); that.p2Layer=createp2singleLayer(); that.layerAction.setLayer(that.p2Layer); that.layerAction.showLayer(); bindCloseEvent(); } } } p2.startp2Layer(); </script> </html>
2. p1.css
/** * Description: * Created by wxy on 2018/2/13 11:02 */ #p2{ width: 500px; height: 300px; background: #ffdd00; color: #fff; position: fixed; top: 50%; left: 50%; transform: translate(-50%,-50%); } #closep2{ cursor: pointer; margin-right: 5px; margin-top: 5px; float: right; border: 1px solid #fff; }
3. p2.css
/** * Description: style of p1 * Created by wxy on 2018/2/13 11:01 */ #p1{ width: 500px; height: 300px; background: #0b0a0a; color: #fff; position: fixed; top: 50%; left: 50%; transform: translate(-50%,-50%); } #closep1{ cursor: pointer; margin-right: 5px; margin-top: 5px; float: right; border: 1px solid #fff; }
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