The Internet Explorer challenge

Detecting IE using the navigator object is challenging because of the “extra” information stored by IE inside both navigator.appVersion and navigator.userAgent.

If we were to use parseFloat to try and extract the browser version, we would get 4.0, instead of 5.5. This is due to the way parseFloat works - it returns the first number it encounters

To retrieve the version number in IE, utilize any combination of string methods that successfully extracts this information. If you're detecting a single IE version (ie: IE 5.5 and NOT IE5.5+), the string method string.indexOf() will work.

//detect IE5.5
if (navigator.appVersion.indexOf("MSIE 5.5")!=-1)
alert("You are using IE5.5!")

However, it is sometimes necessary to determine an entire range of browser versions (IE 5.5 and up, for example). Our suggestion is to invoke the adage "whatever works." Here is our method to detect a version of IE and up:

//Detect IE5.5+
version=0
if (navigator.appVersion.indexOf("MSIE")!=-1){ temp=navigator.appVersion.split("MSIE")
version=parseFloat(temp[1])
}

if (version>=5.5//NON IE browser will return 0
alert("You are using IE5.5+")

In the above, string.split() is first used to divide navigator.appVersion into two parts, using "MSIE" as the separator. As a result, temp[1] contains the code after "MSIE", with the browser version appearing first. Doing a parseFloat() on temp[1] will retrieve the browser version of IE.