browser scroll event control, 控制窗口滚动

browser scroll event

// left: 37, up: 38, right: 39, down: 40,
// spacebar: 32, pageup: 33, pagedown: 34, end: 35, home: 36
    var keys = [37, 38, 39, 40];

    function preventDefault(e) {
        e = e || window.event;
        if (e.preventDefault)
            e.preventDefault();
        e.returnValue = false;
    }

    function keydown(e) {
        for (var i = keys.length; i--;) {
            if (e.keyCode === keys[i]) {
                preventDefault(e);
                return;
            }
        }
    }

    function wheel(e) {
        preventDefault(e);
    }

    function disable_scroll() {
        if (window.addEventListener) {
            window.addEventListener('DOMMouseScroll', wheel, false);
        }
        window.onmousewheel = document.onmousewheel = wheel;
        document.onkeydown = keydown;
    }

    function enable_scroll() {
        if (window.removeEventListener) {
            window.removeEventListener('DOMMouseScroll', wheel, false);
        }
        window.onmousewheel = document.onmousewheel = document.onkeydown = null;
    }