Js used to determine whether the current browser version IE8.0

(function () {
    var DEFAULT_VERSION = "8.0";
    var navigator.userAgent.toLowerCase UA = (); // get the current version of the browser, and the status is lowercase string;
    var = isIE ua.indexOf ( "MSIE ")> --1; // Analyzing browser version contains the string 'mise' string, if contained, the position of this string is returned occurs, if included, return -1;
    var safariVersion;
    iF ( isIE) {
        safariVersion ua.match = (/ MSIE ([\ D.] +) /) [. 1];
    }
    IF (+ safariVersion <= + DEFAULT_VERSION) {
        document.createElement ( 'header');
        document.createElement ( ' NAV ');
        document.createElement (' sectionTop ');
        document.createElement (' footer ');
    }
}) ()