Web移动端使用localStorage缓存Js和css文件

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：

 <script type="text/javascript">
        //入口函数
                if (window.localStorage) {
                    initJs();
                    initCss("css", "/gfdzp201508257998/Turntable/Style/css_whir.css");
                } else {
                    addFile("/gfdzp201508257998/Turntable/Script/jquery-1.8.3.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";
            var url = "/gfdzp201508257998/Turntable/Script/jquery-1.8.3.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 = "turntable";
            var url = "/gfdzp201508257998/Turntable/Script/whir.turntable.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>

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：[email protected]
* 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">
        //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", "/gfdzp201508257998/Turntable/Script/jquery-1.8.3.min.js",
         function () {
             whir.res.loadJs("turntable", "/gfdzp201508257998/Turntable/Script/whir.turntable.js", null);
         });
        whir.res.loadCss("css", "/gfdzp201508257998/Turntable/Style/css_whir.css", null);
    </script>