function addEvent(obj, sEv, fn) {
    if (obj.addEventListener) {
        obj.addEventListener(sEv, fn, false);
    } else {
        obj.attachEvent('on' + sEv, fn);
    }
}
function addWheel(obj, fn) {
    function wheel(ev) {
        var oEvent = ev || event;
        var bDown = true;
        bDown = oEvent.wheelDelta ? oEvent.wheelDelta > 0 : oEvent.detail < 0;
        fn && fn(bDown);
        oEvent.preventDefault && oEvent.preventDefault();
        return false;
    }

    if (window.navigator.userAgent.toLowerCase().indexOf('firefox') != -1) {
        obj.addEventListener('DOMMouseScroll', wheel, false);
    } else {
        addEvent(obj, 'mousewheel', wheel)
    }
}



function wheel(obj) {
    if (!obj) return;
    var oBlock = obj.siderParent,     //滚动条大块
        oBar = obj.siderChild,         //滚动条小块
        oContent = obj.conParent, //大内容
        oPara = obj.conChild;       //小内容


    //小条的大小根据内容大小走
    oBar.css({
        height: (oContent.outerHeight() / oPara.outerHeight()) * oBlock.outerHeight()
    });

    function setTop(t) {
        if (t < 0) {
            t = 0;
        }
        else if (t > oBlock.outerHeight() - oBar.outerHeight()) {
            t = oBlock.outerHeight() - oBar.outerHeight();
        }
        var addWheelScale = t / (oBlock.outerHeight() - oBar.outerHeight());
        oBar.css('top', t);
        oPara.css('top', addWheelScale * (oContent.outerHeight() - oPara.outerHeight()));

    };

    oBar.on('mousedown', function (ev) {
        var disY = ev.clientY - oBar.position().top;
        $(document).on({
            'mousemove': function (ev) {
                var t = ev.clientY - disY;
                setTop(t);
            },
            'mouseup': function () {
                $(document).off('mousemove');
                $(document).off('mouseup');
                oBar[0].releaseCapture && oBar[0].releaseCapture();
            },
        });
        oBar[0].setCapture && oBar[0].setCapture();
        return false;
    });

    $(document).on('keydown', function (ev) {
        var t = oBar.position().top;
        switch (ev.keyCode) {
            case 38:
                t -= 10;
                break;
            case 40:
                t += 10;
                break;
        }
        setTop(t);
    });

    addWheel(oContent[0], function (bDown) {
        var t = oBar.position().top;
        if (bDown) {
            t -= 10;
        } else {
            t += 10;
        }
        setTop(t);
    });
}