To Check Internet Explorer (IE) version

Little helper function to return details about IE 8 and its various compatibility settings either use as it is or incorporate into a browser object. Remember browser sniffing is not the best way to detect user-settings as spoofing is very common so use with caution.


function IEVersion(){
var _n=navigator,_w=window,_d=document;
var version="NA";
var na=_n.userAgent;
var ieDocMode="NA";
var ie8BrowserMode="NA";
// Look for msie and make sure its not opera in disguise
if(/msie/i.test(na) && (!_w.opera)){
// also check for spoofers by checking known IE objects
if(_w.attachEvent && _w.ActiveXObject){
// Get version displayed in UA although if its IE 8 running in 7 or compat mode it will appear as 7
version = (na.match( /.+ie\s([\d.]+)/i ) || [])[1];
// Its IE 8 pretending to be IE 7 or in compat mode
if(parseInt(version)==7){
// documentMode is only supported in IE 8 so we know if its here its really IE 8
if(_d.documentMode){
version = 8; //reset? change if you need to
// IE in Compat mode will mention Trident in the useragent
if(/trident\/\d/i.test(na)){
ie8BrowserMode = "Compat Mode";
// if it doesn't then its running in IE 7 mode
}else{
ie8BrowserMode = "IE 7 Mode";
}
}
}else if(parseInt(version)==8){
// IE 8 will always have documentMode available
if(_d.documentMode){ ie8BrowserMode = "IE 8 Mode";}
}
// If we are in IE 8 (any mode) or previous versions of IE we check for the documentMode or compatMode for pre 8 versions
ieDocMode = (_d.documentMode) ? _d.documentMode : (_d.compatMode && _d.compatMode=="CSS1Compat") ? 7 : 5;//default to quirks mode IE5
}
}

return {
"UserAgent" : na,
"Version" : version,
"BrowserMode" : ie8BrowserMode,
"DocMode": ieDocMode
}
}
var ieVersion = IEVersion();
var IsIE8 = ieVersion.Version != "NA" && ieVersion.Version >= 8;

if (!IsIE8) {
alert("Please upgrade to Internet Explorer 8 or better!" ) ;
}