Detecting IE8 with JavaScript using document.addEventListener

Question

I came across this code in a project I am working on that is used to detect if the browser is IE8:

var isIE8 = function(){ return (!document.addEventListener) ? true : false; };

I don't understand why the conditional operator ? true : false is used to return true if true and false if false. The logical NOT ! is applied to the value of document.addEventListener and will always return a Boolean value, would this not do exactly the same thing:

var isIE8 = function(){ return (!document.addEventListener); };

.addEventListener Browser Compatibility

This Answer was the closest information I could find on this.

Thanks for taking a look :)

Answer 1

If you would just like to detect IE8, checking for addEventListener will do the job. But if you would like to check for IE and its versions in general, I find this method the most intuitive and most useful:

var uA = navigator.userAgent;
var browser = null;
var ieVersion = null; 

if (uA.indexOf('MSIE 6') >= 0) {
    browser = 'IE';
    ieVersion = 6;
}
if (uA.indexOf('MSIE 7') >= 0) {
    browser = 'IE';
    ieVersion = 7;
}
if (document.documentMode) { // as of IE8
    browser = 'IE';
    ieVersion = document.documentMode;
}

You're also catching higher IE versions in Compatibility Mode/View this way. And using the script is very easy:

if ((browser == 'IE') && (ieVersion <= 10)) 
    // do something, for example:
    document.documentElement.className += ' ie10-';