Full window popup menu

app.js

$(function(){
    var scrT;
    $('.menu-trigger').on('click',function(){
        if(!$('#menu-cover').hasClass('is_active')){
            $('.menu-trigger').one('click',openMainMenu());
        } else {
            // console.log(scrT);
            $('.close-holder').one('click',closeMainMenu());
        }
    });
    function openMainMenu(){
        scrT = $(window).scrollTop();
        $('#menu-cover').addClass('is_active');
        $('body').css({
            position: 'fixed',
            width: '100%',
            top: -1 * scrT,
        });
    }
    function closeMainMenu(){
        $('#menu-cover').removeClass('is_active');
        $('body').css({
          position: 'inherit',
          top:'auto',
        });
        $(window).scrollTop(scrT);
    }
});