Javascript: IE Detection

ie_detection.js

var ie = (function (){
    if (window.ActiveXObject === undefined) return null;
    if (!window.XMLHttpRequest) return 6;
    if (!document.querySelector) return 7;
    if (!document.addEventListener) return 8;
    if (!window.atob) return 9;
    if (!document.__proto__) return 10;
    return 11;
})();