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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 = "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);
}

console.log(majorVersion);