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/

jQuery可以很好地处理这个问题(jQuery.browser)

var ua = $.browser;
if ( ua.mozilla && ua.version.slice(0,3) == "1.9" ) {
    alert( "Do stuff for firefox 3" );
}

编辑:正如Joshua在他的评论下面所写的，jQuery。jQuery自1.9版起不再支持browser属性(详情请参阅jQuery 1.9发布说明)。 jQuery开发团队建议使用更完整的方法，例如使用Modernizr库调整UI。

您可以看到浏览器显示的内容，并使用该信息记录或测试多个浏览器。

navigator.sayswho= (function(){ var ua= navigator.userAgent; var tem; var M= ua.match(/(opera|chrome|safari|firefox|msie|trident(?=\/))\/?\s*(\d+)/i) || []; if(/trident/i.test(M[1])){ tem= /\brv[ :]+(\d+)/g.exec(ua) || []; return 'IE '+(tem[1] || ''); } if(M[1]=== 'Chrome'){ tem= ua.match(/\b(OPR|Edge)\/(\d+)/); if(tem!= null) return tem.slice(1).join(' ').replace('OPR', 'Opera'); } M= M[2]? [M[1], M[2]]: [navigator.appName, navigator.appVersion, '-?']; if((tem= ua.match(/version\/(\d+)/i))!= null) M.splice(1, 1, tem[1]); return M.join(' '); })(); console.log(navigator.sayswho); // outputs: `Chrome 62`

使用这个:http://www.quirksmode.org/js/detect.html

alert(BrowserDetect.browser); // will say "Firefox"
alert(BrowserDetect.version); // will say "3" or "4"

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 15+, the true version is after "OPR/" 
if ((verOffset = nAgt.indexOf("OPR/")) != -1) {
    browserName = "Opera";
    fullVersion = nAgt.substring(verOffset + 4);
}
// In older Opera, the true version is after "Opera" or after "Version"
else 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 = "Google 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 = "Mozilla 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);
}

为什么不另一个解决方案:

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