Unable to get property 'refresh' of undefined or null reference error in ie8

Question

My script:

var slidespeed = 200;
$('.noti_user a').off().on('click',function(){
    if($(this).hasClass('active')){
        $(this).removeClass('active');
        $('.sub_menu_closer').hide();
        $('.noti_drop_down').slideUp(slidespeed);
    }else{
        $('.left_user_inner').children('div').children('a').removeClass('active');
        $('.left_logo_part a').removeClass('active')
        $('.help_drop_down,.mail_drop_down').slideUp(slidespeed)
        $('.logo_drop_down').slideUp(slidespeed);
        $('.noti_drop_down').slideDown(slidespeed,function(){
            sScroll.refresh(); // here is error show
        });
        $('.sub_menu_closer').show();
        $(this).addClass('active');
    }
})

var sScroll; // here iscroll call
   sScroll = new IScroll('.noti_outer', {scrollbars: 'custom',mouseWheel: true});
   document.addEventListener('touchmove', function (e) { e.preventDefault(); }, false);

sScroll.refresh(); here is i refresh iScroll plugin

when i testing in ie8 browser this show error : Unable to get property 'refresh' of undefined or null reference

Answer 1

As mentioned above. The IScroll lib is not compatible with older IE versions. Therefore you can't call a method. To prevent the error, you can go like this:

  $('.noti_drop_down').slideDown(slidespeed,function(){
    if (sScroll && typeof sScroll === 'object' && typeof sScroll.refresh === 'function') {
     sScroll.refresh(); // here is error show
    }
  });

This might be to many conditions in the if statement, simply check what sScroll is in IE, if it is undefined, reduce the conditions, but it should avoid the error.