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localStorage缓存Js和css文件实例方法

小云云   2018-02-28 10:53   1535浏览 原创

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(&#39;HEAD&#39;).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(&#39;HEAD&#39;).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:
这里写图片描述

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(&#39;HEAD&#39;).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(&#39;HEAD&#39;).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(&#39;HEAD&#39;).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(&#39;HEAD&#39;).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>

这里写图片描述

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