Create a title tracks while scrolling

Create a title tracks while scrolling

  1. if($('h1').offset().top<='45'){
  2.       $(this).addClass('active');
  3. }
I have no idea why it does not work but I want to create a title tracks like the iPhone's phone book
I work with iscroll4
I tried to build this code
But is not present
Sorry for the English (translation)