用户代理字符串检测脚本，包括检测呈现引擎、平台、windows操

var client = function() {
//显现引擎
var engine = {
    ie: 0,
    gecko: 0,
    webkit: 0,
    khtml: 0,
    opera: 0,
    //完整版本号
    ver: null
};

//浏览器
var browser = {
    //主要浏览器
    ie: 0,
    firefox: 0,
    safari: 0,
    konq: 0,
    opera: 0,
    chrome: 0,
    //具体版本号
    ver:null
};

//平台、设备和操作系统
var system = {
    win: false,
    mac: false,
    xll: false,
    //移动设备
    iphone: false,
    ipod: false,
    ipad: false,
    ios: false,
    android: false,
    nokiaN: false,
    winMobile: false,

    //游戏系统
    wii: false,
    ps: false
};

//检测呈现引擎和浏览器
var ua = navigator.userAgent;
if(window.opera) {
    engine.ver = browser.ver = window.opera.version();
    engine.opera = browser.opera = parseFloat(engine.ver);
} else if (/AppleWebkit\/(\S+)/.test(ua)) {
    engine.ver = RegExp["$1"];//表示与正则表达式匹配的第一个
    engine.webkit = parseFloat(engine.ver);

    //确定是Chrome还是Safari
    if(/Chrome\/(S+)/.test(ua)) {
        browser.ver = RegExp["$1"];
    } 
    else if (/Version\/(S+)/.test(ua)) {
        browser.ver = RegExp["$1"];
        browser.safari = parseFloat(browser.ver);
    } 
    else {
        //近似地确认版本号
        var safariVersion = 1;
        if (engine.webkit < 100) {
            safariVersion = 1;
        } 
        else if (engine.webkit < 312) {
            safariVersion = 1.2;
        } 
        else if (engine.webkit < 412) {
            safariVersion = 1.3;
        } 
        else {
            safariVersion = 2;
        }

        browser.safari = browser.ver = safariVersion;
    } 
}
else if (/KHTML\/(\S+)/.test(ua) || /konqueror\/([^;]+)/.test(ua)) {
    engine.ver = browser.ver = RegExp["$1"];
    engine.khtml = browser.konq = parseFloat(engine.ver);
}
else if (/rv:([^\)]+)\) Gecko\/\d{8}/.test(ua)) {
    engine.ver = RegExp["$1"];
    engine.gecko = parseFloat(engine.ver);

    //确定是不是火狐
    if (/Firefox\/(\S+)/.test(ua)) {
        browser.ver = RegExp["$1"];
        browser.firefox = parseFloat(browser.ver);
    }
}
else if (/MSIE ([^;]+)/.test(ua)) {
    engine.ver = browser.ver = RegExp["$1"];
    engine.ie = browser.ie = parseFloat(engine.ver);
}

//检测浏览器
browser.ie = engine.ie;
browser.opera = engine.opera;

//检测平台
var p = navigator.platform;
system.win = p.indexOf("Win") == 0;
system.mac = p.indexOf("Mac") == 0;
system.xll = (p == "xll") || (p.indexOf("Linux") == 0);

//检测Windows操作系统
if (system.win) {
    if (/Win(?:dows )?([^do]{2})\s?(\d+\.\d+)?/.test(ua)) {
        if (RegExp["$1"] == "NT") {
            switch(RegExp["$2"]) {
                case "5.0":
                    system.win = "2000";
                    break;
                case "5.1":
                    system.win = "XP";
                    break;
                case "6.0":
                    system.win = "Vista";
                    break;
                case "6.1":
                    system.win = "7";
                    break;
                default:
                    system.win = "NT";
                    break;
            }
        }
        else if (RegExp["$1"] == "9x") {
            system.win = "ME";
        }
        else {
            system.win = RegExp["$1"];
        }
    }
}

system.iphone = ua.indexOf("iphone") > -1;
system.ipod = ua.indexOf("iPod") > -1;
system.ipad = ua.indexOf("iPad") > -1;
system.nokiaN = ua.indexOf("NokiaN") > -1;

//windows mobile
if (system.win == "CE") {
    system.winMobile = system.win;
}
else if (system.win == "Ph") {
    if (/Windows phone OS (\d+.\d+)/.test(ua)) {
        system.win = "Phone";
        system.winMobile = parseFloat(RegExp["$1"]);
    }
}

//检测ios版本
if (system.mac && ua.indexOf("Mobile") > -1) {
    if (/CPU (?:iPhone)?OS (\d+_\d+)/.test(ua)) {
        system.ios = parseFloat(RegExp.$1.replace("_", "."));
    }
    else {
        system.ios = 2;//不能真正检测出来，所以只能猜测
    }
}

//检测安卓版本
if (/Android (\d+\.\d)/.test(ua)) {
    system.android = parseFloat(RegExp.$1);
}

//游戏系统
system.wii = ua.indexOf("Wii") < -1;
system.ps = /playstation/i.test(ua);

//返回这些对象
return {
    engine: engine,
    browser: browser,
    system: system
};
}();