Scroll until hit a class / element

scroll.js

<script type="text/javascript">
  jQuery(document).ready(function($){
    $.fn.scrollBottom = function() { 
      return $(document).height() - this.scrollTop() - this.height(); 
    };
    
    $(window).scroll(function () {
      // Pick the element you want to move
      var offset = $('#parent').offset();
      // This is the top of the view
      var docViewTop = $(window).scrollTop();
      // This is the end of the section(?)
      var docViewBottom = docViewTop + $(window).height();
      // This is the start of the next section, should unfix the element at this point
      var elemTop = $('.end-of-fixed').offset().top;
      
      // If top of page is greater than the offset of the element AND less than the end of the section
      if ($(window).scrollTop() > offset.top && docViewBottom < elemTop) {
        $('#parent .child').addClass('fixed');
        // Give the fixed element the width of the parent
        $('.fixed').width($('#parent').width());
      } else {
          $('#parent .child').removeClass('fixed');
      }
    });
  });
</script>