scroll-example.js

function() {
  var isFixed = false;

  $(window).on('scroll', function() {
    if (isFixed && shouldGoToStaticCondition) {
      $(el).removeClass('fixed');
      isFixed = false;
    }
    else if (!isFixed && shouldGoToFixCondition) {
       $(el).addClass('fixed');
       isFixed = true;
    }
  });
}