Edit in JSFiddle

var client = function(){
    //呈现引擎
    var engine = {
        ie: 0,
        gecko: 0,
        webkit: 0,
        khtml: 0,
        opera: 0,

        //完整的版本号
      ver: null
    };

    //浏览器
    var browser = {
        //主要浏览器
      ie: 0,
        firefox: 0,
        safari: 0,
        konq: 0,
        opera: 0,
        chrome: 0,

        //具体的版本号
      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"];
        engine.webkit = parseFloat(engine.ver);

        //确定是Chrome还是Safari
        if(/Chrome\/(\S+)/.test(ua)){
            browser.ver = RegExp["$1"];
            browser.chrome = parseFloat(browser.ver);
        }else if(/Version\/(\S+)/.test(ua)){
            browser.ver = RegExp["$1"];
            browser.safari = parseFloat(browser.ver);
        }else{
            //近似的确定版本号
        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["$"];
        engine.gecko = parseFloat(engine.ver);

        //确定是不是Firefox
        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["$"] == "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"];
            }
        }
    }

    //移动设备
   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; //假设
        }
    }

    //检测Android版本
    if(/Android (\a+\.\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
    };
}();

//显示浏览器信息
for (var i in client.browser){
    alert(i+"="+client.browser[i]);
}

<title> JavaScript高级程序设计-客户端检测 </title>
<body>
</body>