JavaScript使用localStorage缓存Js和css文件
对于WebApp来说，将js css文件缓存到localstorage区可以减少页面在加载时与HTTP请求的交互次数,从而优化页面的加载时间.特别是当移端信号不好高延迟时优化效果还是很显见的
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>
再看看封装通用插件方法:
/** * 插件功能:使用localStorage缓存js和css文件,减少http请求和页面渲染的时间,使用于web移动端H5页面的制作 * 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,当需要更新客户资源时,修改变量值即可 * 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加载的回调函数参数传入,如: * whir.res.loadJs ("jquery","TurnTable/Script/jquery.min.js", * function () { * whir.res.loadJs(name,url,null) * }); */ var whir = window.whir || {}; whir.res = { pageVersion : "",//版本,有页面输入,用语刷新localStorage缓存 loadJs : function (name, url, callback) {//动态加载js文件并缓存 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(); } } } } } 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.XNLHTTP"); } 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里的图片路径需要单独处理 whir.res.writeCss(css); } } } } else { css = css.replace(/images\//g,"style/images/");//css里的图片路径需要单独处理 whir.res.writeCss(css); } } else { whir.res.linkCss(url); } }, writeJs : function (text) {//往页面写入js\脚本 var head = document.getElementsByTagName('HEAD').item(0);//获取head var link = document.createElement("script"); link.type = "text/javascript"; link.innerHTML = text; head.appendChild(link); }, writeCss : function (text) {//往页面写入css样式 var head = document.getElementsByTagName("HEAD").item(0); var link = document.createElement("style"); link.type = "text/css"; link.innerHTML = text; head.appendChild(link); }, linkJs : function (url) {//往页面引入js var head = document.getElementsByTagName('HEAD').item(0);//获取head var link = documenr.createElement("script"); link.type = "text/javascript"; link.src = url; head.appendChild(link); }, linkCss : function (url) {//往页面引入css 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>
电脑端使用localstorage是测试没有问题的,但是用android的apk打包之后,导致localstorage失效,无法进行缓存,查阅资料之后,得知解决方法:
安卓代码:
mWebView.getSettings().setDomStorageEnabled(true); mWebView.getSettings().setAppCacheMaxSize(1024*1024*8); String appCachePath = getApplicationContext().getCacheDir().getAbsolutePath(); mWebView.getSettings().setAppCachePath(appCachePath); mWebView.getSettings().setAllowFileAccess(true); mWebView.getSettings().setAppCacheEnabled(true);
另外：Web移动端使用localStorage缓存Js和css文件 | 强制不要缓存
1.尽量不把js放在onload事件中，而是放在由用户主动触发的事件 2.加时间戳，时间不同则会加载js而非使用缓存 强制不要缓存： <meta http-equiv=Cache-Control content=no-cache /> 必须结合其他： <!-- 禁止浏览器从本地缓存中调阅页面。--> <meta http-equiv="pragram" content="no-cache"> <!--网页不保存在缓存中，每次访问都刷新页面。--> <meta http-equiv="cache-control" content="no-cache, must-revalidate"> <!--同上面意思差不多，必须重新加载页面--> <meta http-equiv="expires" content="0"> <!--网页在缓存中的过期时间为0，一旦网页过期，必须从服务器上重新订阅--> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
转自：https://blog.csdn.net/qq_29132907/article/details/79390605
https://www.cnblogs.com/wwdxf/p/6646649.html
https://www.cnblogs.com/zyjzz/p/6973608.html
