Check if user is using IE

Question

I am calling a function like the one below by click on divs with a certain class.

Is there a way I can check when starting the function if a user is using Internet

Answer 1

Update to SpiderCode's answer to fix issues where the string 'MSIE' returns -1 but it matches 'Trident'. It used to return NAN, but now returns 11 for that version of IE.

   function msieversion() {
       var ua = window.navigator.userAgent;
       var msie = ua.indexOf("MSIE ");
       if (msie > -1) {
           return ua.substring(msie + 5, ua.indexOf(".", msie));
       } else if (navigator.userAgent.match(/Trident.*rv\:11\./)) {
           return 11;
       } else {
           return false;
       }
    }