用js实现的检测浏览器和系统的函数

var sUserAgent = navigator.userAgent; 
var fAppVersion = parseFloat(navigator.appVersion); 
function compareVersions(sVersion1, sVersion2) { 
var aVersion1 = sVersion1.split("."); 
var aVersion2 = sVersion2.split("."); 
if (aVersion1.length > aVersion2.length) { 
for (var i=0; i < aVersion1.length - aVersion2.length; i++) { 
aVersion2.push("0"); 
} 
} else if (aVersion1.length < aVersion2.length) { 
for (var i=0; i < aVersion2.length - aVersion1.length; i++) { 
aVersion1.push("0"); 
} 
} 
for (var i=0; i < aVersion1.length; i++) { 
if (aVersion1 < aVersion2) { 
return -1; 
} else if (aVersion1 > aVersion2) { 
return 1; 
} 
} 
return 0; 
} 
var isOpera = sUserAgent.indexOf("Opera") > -1; 
var isMinOpera4 = isMinOpera5 = isMinOpera6 = isMinOpera7 = isMinOpera7_5 = false; 
if (isOpera) { 
var fOperaVersion; 
if(navigator.appName == "Opera") { 
fOperaVersion = fAppVersion; 
} else { 
var reOperaVersion = new RegExp("Opera (\\d+\\.\\d+)"); 
reOperaVersion.test(sUserAgent); 
fOperaVersion = parseFloat(RegExp["$1"]); 
} 
isMinOpera4 = fOperaVersion >= 4; 
isMinOpera5 = fOperaVersion >= 5; 
isMinOpera6 = fOperaVersion >= 6; 
isMinOpera7 = fOperaVersion >= 7; 
isMinOpera7_5 = fOperaVersion >= 7.5; 
} 
var isKHTML = sUserAgent.indexOf("KHTML") > -1 
|| sUserAgent.indexOf("Konqueror") > -1 
|| sUserAgent.indexOf("AppleWebKit") > -1; 
var isMinSafari1 = isMinSafari1_2 = false; 
var isMinKonq2_2 = isMinKonq3 = isMinKonq3_1 = isMinKonq3_2 = false; 
if (isKHTML) { 
isSafari = sUserAgent.indexOf("AppleWebKit") > -1; 
isKonq = sUserAgent.indexOf("Konqueror") > -1; 
if (isSafari) { 
var reAppleWebKit = new RegExp("AppleWebKit\\/(\\d+(?:\\.\\d*)?)"); 
reAppleWebKit.test(sUserAgent); 
var fAppleWebKitVersion = parseFloat(RegExp["$1"]); 
isMinSafari1 = fAppleWebKitVersion >= 85; 
isMinSafari1_2 = fAppleWebKitVersion >= 124; 
} else if (isKonq) { 
var reKonq = new RegExp("Konqueror\\/(\\d+(?:\\.\\d+(?:\\.\\d)?)?)"); 
reKonq.test(sUserAgent); 
isMinKonq2_2 = compareVersions(RegExp["$1"], "2.2") >= 0; 
isMinKonq3 = compareVersions(RegExp["$1"], "3.0") >= 0; 
isMinKonq3_1 = compareVersions(RegExp["$1"], "3.1") >= 0; 
isMinKonq3_2 = compareVersions(RegExp["$1"], "3.2") >= 0; 
} 
} 
var isIE = sUserAgent.indexOf("compatible") > -1 
& sUserAgent.indexOf("MSIE") > -1 
& !isOpera; 
var isMinIE4 = isMinIE5 = isMinIE5_5 = isMinIE6 = isMinIE7 = false; 
if (isIE) { 
var reIE = new RegExp("MSIE (\\d+\\.\\d+);"); 
reIE.test(sUserAgent); 
var fIEVersion = parseFloat(RegExp["$1"]); 
isMinIE4 = fIEVersion >= 4; 
isMinIE5 = fIEVersion >= 5; 
isMinIE5_5 = fIEVersion >= 5.5; 
isMinIE6 = fIEVersion >= 6.0; 
isMinIE7 = fIEVersion >= 7.0; 
} 
var isMoz = sUserAgent.indexOf("Gecko") > -1 
& !isKHTML; 
var isMinMoz1 = sMinMoz1_4 = isMinMoz1_5 = isMinMozl_5_1 = false; 
if (isMoz) { 
var reMoz = new RegExp("rv\\d+\\.\\d+(?:\\.\\d+)?)"); 
reMoz.test(sUserAgent); 
isMinMoz1 = compareVersions(RegExp["$1"], "1.0") >= 0; 
isMinMoz1_4 = compareVersions(RegExp["$1"], "1.4") >= 0; 
isMinMoz1_5 = compareVersions(RegExp["$1"], "1.5") >= 0; 
isMinMoz2 = compareVersions(RegExp["$1"], "1.8") >=0; 
} 
var isNS4 = !isIE & !isOpera && !isMoz && !isKHTML 
& (sUserAgent.indexOf("Mozilla") == 0) 
& (navigator.appName == "Netscape") 
& (fAppVersion >= 4.0 && fAppVersion < 5.0); 
var isMinNS4 = isMinNS4_5 = isMinNS4_7 = isMinNS4_8 = false; 
if (isNS4) { 
isMinNS4 = true; 
isMinNS4_5 = fAppVersion >= 4.5; 
isMinNS4_7 = fAppVersion >= 4.7; 
isMinNS4_8 = fAppVersion >= 4.8; 
} 
var isWin = (navigator.platform == "Win32") || (navigator.platform == "Windows"); 
var isMac = (navigator.platform == "Mac68K") || (navigator.platform == "MacPPC") 
|| (navigator.platform == "Macintosh"); 
var isUnix = (navigator.platform == "X11") & !isWin && !isMac; 
var isWin95 = isWin98 = isWinNT4 = isWin2K = isWinME = isWinXP = isWin03 = false; 
var isMac68K = isMacPPC = false; 
var isSunOS = isMinSunOS4 = isMinSunOS5 = isMinSunOS5_5 = false; 
if (isWin) { 
isWin95 = sUserAgent.indexOf("Win95") > -1 
|| sUserAgent.indexOf("Windows 95") > -1; 
isWin98 = sUserAgent.indexOf("Win98") > -1 
|| sUserAgent.indexOf("Windows 98") > -1; 
isWinME = sUserAgent.indexOf("Win 9x 4.90") > -1 
|| sUserAgent.indexOf("Windows ME") > -1; 
isWin2K = sUserAgent.indexOf("Windows NT 5.0") > -1 
|| sUserAgent.indexOf("Windows 2000") > -1; 
isWinXP = sUserAgent.indexOf("Windows NT 5.1") > -1 
|| sUserAgent.indexOf("Windows XP") > -1; 
isWinNT4 = sUserAgent.indexOf("WinNT") > -1 
|| sUserAgent.indexOf("Windows NT") > -1 
|| sUserAgent.indexOf("WinNT4.0") > -1 
|| sUserAgent.indexOf("Windows NT 4.0") > -1 
& (!isWinME && !isWin2K && !isWinXP); 
isWin03 = sUserAgent.intexOf("Windows NT 5.2") > -1 
} 
if (isMac) { 
isMac68K = sUserAgent.indexOf("Mac_68000") > -1 
|| sUserAgent.indexOf("68K") > -1; 
isMacPPC = sUserAgent.indexOf("Mac_PowerPC") > -1 
|| sUserAgent.indexOf("PC") > -1; 
} 
if (isUnix) { 
isSunOS = sUserAgent.indexOf("SunOS") > -1; 
if (isSunOS) { 
var reSunOS = new RegExp("SunOS (\\d+\\.\\d+(?:\\.\\d+)?)"); 
reSunOS.test(sUserAgent); 
isMinSunOS4 = compareVersions(RegExp["$1"], "4.0") >= 0; 
isMinSunOS5 = compareVersions(RegExp["$1"], "5.0") >= 0; 
isMinSunOS5_5 = compareVersions(RegExp["$1"], "5.5") >= 0; 
} 
}