Onscroll 切换无法添加或删除类

Question

I am fairly new to js but I am trying to get this to fire so that my nav div will stick to the top of the screen I am not sure if my window on the scroll function is firing correctly.

$(document).ready(function() {
  "use strict";

  $('#commons').window.onscroll(function(direction) {
    $('.main-nav').toggleClass('fixed-nav', direction == 'down');
    $('.main-nav a').removeClass('active');
    $('.main-nav a.commons-btn').addClass('active');
  }, {
    offset: '90px'
  });
});

Answer 1

$(document).ready(function(){       
    var scroll_pos = 0;
    $(document).scroll(function() { 
        scroll_pos = $(this).scrollTop();
        if(scroll_pos > 210) {
             // Type here your script, this will run on scrolling
        } else {
            // This script will run when the scroll bar is on the top 
        }
    });
});