Detect IE version (prior to v9) in JavaScript

Question

I want to bounce users of our web site to an error page if they\'re using a version of Internet Explorer prior to v9. It\'s just not worth our time and money to

Answer 1

If nobody else has added an addEventLister-method and you're using the correct browser mode then you could check for IE 8 or less with

if (window.attachEvent && !window.addEventListener) {
    // "bad" IE
}

Legacy Internet Explorer and attachEvent (MDN)