Add class onscroll combined with onepage-scroll.js plug-in

I'm currently using the onepage-scroll.js (https://github.com/peachananr/onepage-scroll) plug-in on my website to scroll through the homepage. When scrolling past the first "slide" I would also like to add a class (sticky) to my header to change some CSS. I've tried the code below, but I can't seem to get it working and I'm kinda in the dark here on how to make this solution work.

var header = $("header");
$("#sliders").scroll(function() {    
    var scroll = $('#sliders').scrollTop();

    console.log(scroll);
        if (scroll >= 50) {
            header.addClass("sticky");
        } else {
            header.removeClass("sticky");
    }
});

Try to make it on document ready. Down only my example worked code on onepage-scroll.js

$(document).ready(function(){
                $(".main").onepage_scroll({
                    sectionContainer: ".sectionscroll",
                    responsiveFallback: 600,
                    loop: true,
                    afterMove:function (index){
                            if ((index == 2)||(index == 3)){
                                        $('#main').addClass('darktheme');
                                    }else{
                                        $('#main').removeClass('darktheme');
                                    }
                    }
                });
                //$(".main").moveTo(2);
                $(".btn-list-bottom").click(function(){$(".main").moveTo(4)});
            });

All you section must have the same class.