javascript浏览器用户代理检测脚本实现方法

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,   x11: 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Chroeme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 {    // 近似地确定版本号     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["$1"];   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.x11 = (p == "x11") || (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"];    }   }  }   // 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 (?:Phone )?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Android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    };   // console.log(engine);  // console.log(browser);  // console.log(system); }();