javascript判定不同浏览器

除了另无它法，肯定不使用navigator.userAgent来判定浏览器。因为在第一次浏览器大战初期，Netscape占绝对统计地位，大部分人们不愿意兼容其他浏览器，并通过检测其UA让他们的网站只允许Netscape访问，这就逼使其他浏览器（包括IE）修改自己的UA伪装成Netscape来通过那些自以为是的脚本，于是出现每个人都声称自己是别人的局面，即使最新的IE9的UA也是:

//Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; Trident/5.0)

//2010 4 16日更新

        ie = !+"\v1" ;

        ie = !-[1,];//IE9预览版中失效

        ie ='\v'=='v' ;

        ie = !!document.recalc

        ie = !!window.VBArray

        ie = !!window.ActiveXObject

        ie = 0//@cc_on+1;

        ie = !!window.createPopup;

        ie = /*@cc_on!@*/!1;

        ie = document.expando;//document.all在opera firefox的古老版本也存在

        ie = /\w/.test('\u0130') //由群里的abcd友情提供

        

        ie6 = !"1"[0] //利用IE6或IE5的字符串不能使用数组下标的特征

        ie8 = !!window.XDomainRequest;

        ie9 =  document.documentMode && document.documentMode === 9;

        //自创，基于条件编译的嗅探脚本，IE会返回其JS引擎的版本号，非IE返回0

        var ieVersion = eval("''+/*@cc_on"+" @_jscript_version@*/-0")*1

        ie9 = ieVersion === 5.9

        ie8 = ieVersion === 5.8

        ie7 = ieVersion === 5.7

        ie6 = ieVersion === 5.6

        ie5 = ieVersion === 5.5

        //https://developer.mozilla.org/En/Windows_Media_in_Netscape

        netscape = !!window.GeckoActiveXObject

        gecko  = !!window.netscape //包括firefox

        firefox = !!window.Components

        firefox = !!window.updateCommands

        safari = !!(navigator.vendor && navigator.vendor.match(/Apple/))

        safari = window.openDatabase && !window.chrome;

        chrome= !!(window.chrome && window.google)

        opera=!!window.opera ;

        //傲游2 3

        maxthon = /maxthon/i.test(navigator.userAgent)

        //360安全浏览器

        is360se = /360se/i.test(navigator.userAgent)

//2010.6.4

       setTimeout(function(){//FF的setTimeout总是有一个额余的参数0

          var isFF = !!arguments.length;

          alert(isFF)

        }, 0);

//判定IE版本

2010.10.1

      ie = (function(undefined){

        var v = 3, div = document.createElement('div');

        while (

        div.innerHTML = '<!--[if gt IE '+(++v)+']><i></i><![endif]-->',

        div.getElementsByTagName('i')[0]);

        return v> 4 ? v : undefined;

      }());

//判定IE版本 2011.2.24

       ie = (function() {

          var v = 3, div = document.createElement('div'), a = div.all || [];

          while (div.innerHTML = '<!--[if gt IE '+(++v)+']><br><![endif]-->', a[0]);

          return v > 4 ? v : !v;

        }());

//手机的相关判定 2011.9.21

 isIPhone = /iPhone/i.test(navigator.userAgent);

 isIPhone4 = window.devicePixelRatio >= 2

//在网页中，pixel与point比值称为device-pixel-ratio，普通设备都是1，iPhone 4是2，有些Android机型是1.5

//http://blog.webcreativepark.net/2011/01/25-173502.html

 isIPad = /iPad/i.test(navigator.userAgent);

 isAndroid = /android/i.test(navigator.userAgent);

 isIOS = isIPhone  || isIPad ;

isMobile = isIOS || isAndroid ;