document.addEventListener("DOMContentLoaded", function() {
    //The first argument are the elements to which the plugin shall be initialized
    //The second argument has to be at least a empty object or a object with your desired options
    OverlayScrollbars(document.querySelectorAll('body'), { });
});

$(function() {
    //The passed argument has to be at least a empty object or a object with your desired options
    $('body').overlayScrollbars({ });
});