IE detection in JavaScript

ie-detect.js

function msieversion() {
    var ua = window.navigator.userAgent,
        msie = ua.indexOf("MSIE ");

    // If IE, alert version
    if (msie > 0 || !!navigator.userAgent.match(/Trident.*rv\:11\./))
        alert(parseInt(ua.substring(msie + 5, ua.indexOf(".", msie))));
    else
        alert('otherbrowser');
    
    return false;
}