js monitor web page and scroll down event, a navigation bar automatically show or hide

/ ** 
* page and scroll down event 
* @param e 
* / 
// 0 is hidden, a display 
var S = 1; 

function scrollFunc (e) { 
    // e presence does not exist on the use of e with windon.event 
    e = the window.event || E; 
// first determine what browser 
    iF (e.wheelDelta) { 
        // browser IE, Google 
        iF (e.wheelDelta> 0) { 
// when scrolling up when the pulley 
// console.log ( "scroll up pulley"); 
            IF (S == 0) { 
                // slide down 
                $ ( "Div2.") slideDown ( "SLOW");. 
                S =. 1; 
            } 
        } 
        IF (e.wheelDelta <0) { 
// when scrolling down pulley 
// the console.log ( "scroll down pulley");
            IF (S ==. 1) { 
                // slid up
                $ ( "Div2.") slideUp ( "SLOW");. 
                S = 0; 
            } 
        } 
    } the else IF (e.detail) { 
        // browser Firefox 
        IF (e.detail> 0) { 
// when the pulley scroll up when 
// console.log ( "scroll up pulley"); 
            IF (S == 0) { 
                // slide down 
                $ ( "Div2.") slideDown ( "SLOW");. 
                S =. 1; 
            } 
        } 
        IF ( e.detail <0) { 
            // when scrolling down pulley 
            // console.log ( "scroll down pulley"); 
            iF (S ==. 1) { 
                // slide upward 
                $ ( "div2.") slideUp . ( "slow");
                s = 0;
            }
        } 
    } 
} 

// bind to the page scroll wheel event 
IF (document.addEventListener) { 
    // Firefox browser 
    document.addEventListener ( 'DOMMouseScroll', scrollFunc, false); 
} 
// IE browser Google 
window.onmousewheel = document. onmousewheel = scrollFunc;