为什么不另一个解决方案:

navigator.userAgent.includes("Firefox")? log("Mozilla") :log("Chrome")

看看navigator。userAgent - Firefox/xxx.xxx. xxx。XXX是在结尾指定的。

我用ASP代码做了一个检测浏览器，浏览器版本，OS和OS版本的脚本。 我在ASP中这样做的原因是因为我想将数据存储在日志数据库中。 所以我必须检测浏览器服务器端。

代码如下:

on error resume next
ua = lcase(Request.ServerVariables("HTTP_USER_AGENT"))
moz = instr(ua,"mozilla")  
ffx = instr(ua,"firefox")  
saf = instr(ua,"safari")
crm = instr(ua,"chrome") 
max = instr(ua,"maxthon") 
opr = instr(ua,"opera")
ie4 = instr(ua,"msie 4") 
ie5 = instr(ua,"msie 5") 
ie6 = instr(ua,"msie 6") 
ie7 = instr(ua,"msie 7") 
ie8 = instr(ua,"trident/4.0")
ie9 = instr(ua,"trident/5.0")

if moz>0 then 
    BrowserType = "Mozilla"
    BrVer = mid(ua,moz+8,(instr(moz,ua," ")-(moz+8)))
end if
if ffx>0 then 
    BrowserType = "FireFox"
    BrVer = mid(ua,ffx+8)
end if
if saf>0 then 
    BrowserType = "Safari"
    BrVerPlass = instr(ua,"version")
    BrVer = mid(ua,BrVerPlass+8,(instr(BrVerPlass,ua," ")-(BrVerPlass+8)))
end if
if crm>0 then 
    BrowserType = "Chrome"
    BrVer = mid(ua,crm+7,(instr(crm,ua," ")-(crm+7)))
end if
if max>0 then 
    BrowserType = "Maxthon"
    BrVer = mid(ua,max+8,(instr(max,ua," ")-(max+8)))
end if
if opr>0 then 
    BrowserType = "Opera"
    BrVerPlass = instr(ua,"presto")
    BrVer = mid(ua,BrVerPlass+7,(instr(BrVerPlass,ua," ")-(BrVerPlass+7)))
end if
if ie4>0 then 
    BrowserType = "Internet Explorer"
    BrVer = "4"
end if
if ie5>0 then 
    BrowserType = "Internet Explorer"
    BrVer = "5"
end if
if ie6>0 then 
    BrowserType = "Internet Explorer"
    BrVer = "6"
end if
if ie7>0 then 
    BrowserType = "Internet Explorer"
    BrVer = "7"
end if
if ie8>0 then 
    BrowserType = "Internet Explorer"
    BrVer = "8"
    if ie7>0 then BrVer = BrVer & " (in IE7 compability mode)"
end if
if ie9>0 then 
    BrowserType = "Internet Explorer"
    BrVer = "9"
    if ie7>0 then BrVer = BrVer & " (in IE7 compability mode)"
    if ie8>0 then BrVer = BrVer & " (in IE8 compability mode)"
end if

OSSel = mid(ua,instr(ua,"(")+1,(instr(ua,";")-instr(ua,"("))-1)
OSver = mid(ua,instr(ua,";")+1,(instr(ua,")")-instr(ua,";"))-1)

if BrowserType = "Internet Explorer" then
    OSStart = instr(ua,";")
    OSStart = instr(OSStart+1,ua,";")        
    OSStopp = instr(OSStart+1,ua,";")
    OSsel = mid(ua,OSStart+2,(OSStopp-OSStart)-2)
end if

    Select case OSsel
        case "windows nt 6.1"
            OS = "Windows"
            OSver = "7"
        case "windows nt 6.0"
            OS = "Windows"
            OSver = "Vista"
        case "windows nt 5.2"
            OS = "Windows"
            OSver = "Srv 2003 / XP x64"
        case "windows nt 5.1"
            OS = "Windows"
            OSver = "XP"
        case else
            OS = OSSel
    End select

Response.write "<br>" & ua & "<br>" & BrowserType & "<br>" & BrVer & "<br>" & OS & "<br>" & OSver & "<br>"

'Use the variables here for whatever you need........

var nVer = navigator.appVersion;
var nAgt = navigator.userAgent;
var browserName  = navigator.appName;
var fullVersion  = ''+parseFloat(navigator.appVersion);
var majorVersion = parseInt(navigator.appVersion,10);
var nameOffset,verOffset,ix;

// In Opera, the true version is after "Opera" or after "Version"

if ((verOffset=nAgt.indexOf("Opera"))!=-1) {
 browserName = "Opera";
 fullVersion = nAgt.substring(verOffset+6);
 if ((verOffset=nAgt.indexOf("Version"))!=-1)
   fullVersion = nAgt.substring(verOffset+8);
}
// In MSIE, the true version is after "MSIE" in userAgent

else if ((verOffset=nAgt.indexOf("MSIE"))!=-1) {
 browserName = "Microsoft Internet Explorer";
 fullVersion = nAgt.substring(verOffset+5);
}
// In Chrome, the true version is after "Chrome"

else if ((verOffset=nAgt.indexOf("Chrome"))!=-1) {
 browserName = "Chrome";
 fullVersion = nAgt.substring(verOffset+7);
}
// In Safari, the true version is after "Safari" or after "Version"

else if ((verOffset=nAgt.indexOf("Safari"))!=-1) {
 browserName = "Safari";
 fullVersion = nAgt.substring(verOffset+7);
 if ((verOffset=nAgt.indexOf("Version"))!=-1)
   fullVersion = nAgt.substring(verOffset+8);
}
// In Firefox, the true version is after "Firefox"

else if ((verOffset=nAgt.indexOf("Firefox"))!=-1) {
 browserName = "Firefox";
 fullVersion = nAgt.substring(verOffset+8);
}
// In most other browsers, "name/version" is at the end of userAgent

else if ( (nameOffset=nAgt.lastIndexOf(' ')+1) <
          (verOffset=nAgt.lastIndexOf('/')) )
{
 browserName = nAgt.substring(nameOffset,verOffset);
 fullVersion = nAgt.substring(verOffset+1);
 if (browserName.toLowerCase()==browserName.toUpperCase()) {
  browserName = navigator.appName;
 }
}

// trim the fullVersion string at semicolon/space if present

if ((ix=fullVersion.indexOf(";"))!=-1)
   fullVersion=fullVersion.substring(0,ix);
if ((ix=fullVersion.indexOf(" "))!=-1)
   fullVersion=fullVersion.substring(0,ix);

majorVersion = parseInt(''+fullVersion,10);
if (isNaN(majorVersion)) {
 fullVersion  = ''+parseFloat(navigator.appVersion);
 majorVersion = parseInt(navigator.appVersion,10);
}

document.write(''
 +'Browser name  = '+browserName+'<br>'
 +'Full version  = '+fullVersion+'<br>'
 +'Major version = '+majorVersion+'<br>'
 +'navigator.appName = '+navigator.appName+'<br>'
 +'navigator.userAgent = '+navigator.userAgent+'<br>'
)

看这里的演示..http://jsfiddle.net/hw4jM/3/

var ua = navigator.userAgent;

if (/Firefox\//.test(ua))
   var Firefox = /Firefox\/([0-9\.A-z]+)/.exec(ua)[1];

浏览器JavaScript库提供了此功能。

if (bowser.msie && bowser.version <= 6) {
  alert('Hello China');
}

它似乎保养得很好。