localStorage缓存Js和css文件实例方法
2020-11-27
来源：星星旅游
将jquery和公共样式缓存到localStorage，可以减少Http请求，从而优化页面加载时间，下面的代码可以实现此功能：
<!DOCTYPE html><html lang="en"><head>
<meta charset="UTF-8">
<title>Document</title></head><body>
<!--
1.缓存css、js到LocalStorage
2.调用本地缓存css/js拼接到HTML页面
-->
<script type="text/javascript">
//入口函数
if (window.localStorage) {
initJs();
initCss("css", "reset.css");
} else {
alert("不能使用本地缓存");
addFile("http://libs.baidu.com/jquery/2.0.0/jquery.min.js", "js");
addFile("/gfdzp201508257998/Turntable/Script/whir.turntable.js", "js");
addFile("/gfdzp201508257998/Turntable/Style/css_whir.css", "css");
} //第一步：加载页面js：先加载jQuery后加载用户脚本
function initJs() {
var name = "jquery";//存储key的name
var url = "js/jquery-1.9.1.min.js"; var xhr; var js = window.localStorage ? localStorage.getItem(name) : ""; if (js == null || js.length == 0) { if (window.ActiveXObject) {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
} else if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
}
xhr.open("GET", url);
xhr.send(null);
xhr.onreadystatechange = function () {
if (xhr.readyState == 4 && xhr.status == 200) {
js = xhr.responseText;
localStorage.setItem(name, js);
js = js == null ? "" : js;
addTxt(js, "js");
initTurntable(); //确保先引用Jquery
}
};
} else {
addTxt(js, "js");
initTurntable();
}
} //加载自定义脚本
function initTurntable() {
var name = "zidingyi"; var url = "js/zidingyi.js"; var xhr; var js = window.localStorage ? localStorage.getItem(name) : ""; if (js == null || js.length == 0) { if (window.ActiveXObject) {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
} else if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
}
xhr.open("GET", url);
xhr.send(null);
xhr.onreadystatechange = function () {
if (xhr.readyState == 4 && xhr.status == 200) {
js = xhr.responseText;
localStorage.setItem(name, js);
js = js == null ? "" : js;
addTxt(js, "js");
}
};
} else {
addTxt(js, "js");
}
} //第二步：初始化Css
function initCss(name, url) {
var xhr; var css = window.localStorage ? localStorage.getItem(name) : ""; if (css == null || css.length == 0) { if (window.ActiveXObject) {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
} else if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
}
xhr.open("GET", url);
xhr.send(null);
xhr.onreadystatechange = function () {
if (xhr.readyState == 4 && xhr.status == 200) {
css = xhr.responseText;
localStorage.setItem(name, css);
css = css == null ? "" : css;
css = css.replace(/images\//g, "style/images/");
addTxt(css, "css");
}
};
} else {
css = css.replace(/images\//g, "style/images/");
addTxt(css, "css");
}
} //辅助方法1：动态添加js，css文件引用
function addFile(url, fileType) {
var head = document.getElementsByTagName('HEAD').item(0); var link; if (fileType == "js") {
link = document.createElement("script");
link.type = "text/javascript";
link.src = url;
} else {
link = document.createElement("link");
link.type = "text/css";
link.rel = "stylesheet";
link.rev = "stylesheet";
link.media = "screen";
link.href = url;
}
head.appendChild(link);
} //辅助方法2：动态添加js，css文件内容
function addTxt(text, fileType) {
var head = document.getElementsByTagName('HEAD').item(0); var link; if (fileType == "js") {
link = document.createElement("script");
link.type = "text/javascript";
link.innerHTML = text;
} else {
link = document.createElement("style");
link.type = "text/css";
link.innerHTML = text;
}
head.appendChild(link);
} </script></body></html>查看写入记录： 
封装成JS插件：
/** * 插件功能：使用localStorage缓存js和css文件，减少http请求和页面渲染时间，适用于Web移动端H5页面制作。 * 插件作者：zhangqs008@163.com * 使用方法： * 1.使用此插件前，需要给插件的pageVersion变量赋值，建议变量值由服务器后端输出，当需要更新客户端资源时，修改版本值即可。 * 2.加载Js：由于js加载有顺序要求，所以需要将后加载的脚本作为前一个脚本的回调参数传入，如： * whir.res.loadJs("jquery", "<%= BasePath %>Turntable/Script/jquery-1.8.3.min.js", * function () { * whir.res.loadJs("turntable", "Script/whir.turntable.js", null); * }); * 3.加载css，如：whir.res.loadCss("css", "/Style/css_whir.css", null); */var whir = window.whir || {}; whir.res = { pageVersion: "", //页面版本，由页面输出，用于刷新localStorage缓存 //动态加载js文件并缓存 loadJs: function (name, url, callback) { if (window.localStorage) { var xhr; var js = localStorage.getItem(name); if (js == null || js.length == 0 || this.pageVersion != localStorage.getItem("version")) { if (window.ActiveXObject) { xhr = new ActiveXObject("Microsoft.XMLHTTP"); } else if (window.XMLHttpRequest) { xhr = new XMLHttpRequest(); } if (xhr != null) { xhr.open("GET", url); xhr.send(null); xhr.onreadystatechange = function () { if (xhr.readyState == 4 && xhr.status == 200) { js = xhr.responseText; localStorage.setItem(name, js); localStorage.setItem("version", whir.res.pageVersion); js = js == null ? "" : js; whir.res.writeJs(js); if (callback != null) { callback(); //回调，执行下一个引用 } } }; } } else { whir.res.writeJs(js); if (callback != null) { callback(); //回调，执行下一个引用 } } } else { whir.res.linkJs(url); } }, loadCss: function (name, url) { if (window.localStorage) { var xhr; var css = localStorage.getItem(name); if (css == null || css.length == 0 || this.pageVersion != localStorage.getItem("version")) { if (window.ActiveXObject) { xhr = new ActiveXObject("Microsoft.XMLHTTP"); } else if (window.XMLHttpRequest) { xhr = new XMLHttpRequest(); } if (xhr != null) { xhr.open("GET", url); xhr.send(null); xhr.onreadystatechange = function () { if (xhr.readyState == 4 && xhr.status == 200) { css = xhr.responseText; localStorage.setItem(name, css); localStorage.setItem("version", whir.res.pageVersion); css = css == null ? "" : css; css = css.replace(/images\//g, "style/images/"); //css里的图片路径需单独处理 whir.res.writeCss(css); } }; } } else { css = css.replace(/images\//g, "style/images/"); //css里的图片路径需单独处理 whir.res.writeCss(css); } } else { whir.res.linkCss(url); } }, //往页面写入js脚本 writeJs: function (text) { var head = document.getElementsByTagName('HEAD').item(0); var link = document.createElement("script"); link.type = "text/javascript"; link.innerHTML = text; head.appendChild(link); }, //往页面写入css样式 writeCss: function (text) { var head = document.getElementsByTagName('HEAD').item(0); var link = document.createElement("style"); link.type = "text/css"; link.innerHTML = text; head.appendChild(link); }, //往页面引入js脚本 linkJs: function (url) { var head = document.getElementsByTagName('HEAD').item(0); var link = document.createElement("script"); link.type = "text/javascript"; link.src = url; head.appendChild(link); }, //往页面引入css样式 linkCss: function (url) { var head = document.getElementsByTagName('HEAD').item(0); var link = document.createElement("link"); link.type = "text/css"; link.rel = "stylesheet"; link.rev = "stylesheet"; link.media = "screen"; link.href = url; head.appendChild(link); } }
调用该插件：
<script type="text/javascript" src="fengzhuang.js"></script>
<script type="text/javascript">
//入口函数
whir.res.pageVersion = "1002"; //页面版本，用于检测是否需要更新缓存
whir.res.loadJs("jquery", "js/jquery-1.9.1.min.js", function () {
whir.res.loadJs("zidingyi", "js/zidingyi.js", null);
});
whir.res.loadCss("css", "reset.css", null); </script>