How can you detect the version of a browser?

Question

I\'ve been searching around for code that would let me detect if the user visiting the website has Firefox 3 or 4. All I have found is code to detect the type of browser but

Answer 1

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);
}