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proxyMode.html
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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>代理模式</title>
</head>
<body>
<div class="title">
开发中最常见的四种代理类型：事件代理、虚拟代理、缓存代理和保护代理
</div>
<div id="father">
<a href="#">连接1号</a>
<a href="#">连接2号</a>
<a href="#">连接3号</a>
<a href="#">连接4号</a>
<a href="#">连接5号</a>
</div>
<script>
// 事件代理
function getClickText() {
let father = document.getElementById('father');
father.addEventListener('click', (ev) => {
let nodeName = ev.target.nodeName;
if (nodeName === 'A') {
console.log(ev.target.innerText);
ev.preventDefault();
}
})
}
getClickText();
// 虚拟代理模式
class PreLoadImgage{
constructor (imgNode) {
this.imgNode = imgNode;
}
// 操作img节点的src属性
setImgSrc (imgUrl = '') {
this.imgNode.src = imgUrl;
}
}
class ProxyImgage {
// 占位符的url地址
static LOADING_URL = 'xxxxxx';
constructor(targetImage) {
// 目标Imgage即PreLoadImgage实例
this.targetImage = targetImage;
}
// 该方法主要操作虚拟Image,完成加载
setSrc(targetUrl) {
// 真实img节点初始化展示的是一个占位符
this.targetImage.setSrc(ProxyImgage.LOADING_URL);
// 创建一个加载图片的虚拟Image实例
const virtualImage = new Image();
// 监听虚拟Image图片的加载情况，完成加载后设置真实的img节点图片路径
virtualImage.onload = () => {
this.targetImage.setSrc(targetUrl);
}
// 设置虚拟Image的图片路径
virtualImage.src = targetUrl;
}
}
// 缓存代理模式
/**
* 传进来的所有参数进行进行求和运算
*/
const addAll = function() {
let result = 0;
let len = arguments.length;
for (let k = 0; k < len; k++) {
const item = arguments[k];
result += item;
}
return result;
}
/**
* 为求和方法创建的代理
*/
const proxAddAll = (function() {
// 缓存变量
const resultCache = {};
return function() {
const args = Array.prototype.join.call(arguments, ',');
console.log(args, '----------'); // 1,2,3,4,5,6,7,3,4,8,10,11
// 判断缓存变量中是否存在对应的计算结果
if (args in resultCache) {
return resultCache[args]; // 64
}
return resultCache[args] = addAll(...arguments);
}
})();
console.log(proxAddAll(1,2,3,4,5,6,7,3,4,8,10,11));
console.log(proxAddAll(1,2,3,4,5,6,7));
console.log(proxAddAll(1,2,3,4,5,6,7,3,4,8,10,11));
console.log(proxAddAll(1,2,3,4,5,6,7));
</script>
</body>
</html>