1$(document.body).on('touchmove', onScroll); // for mobile
2$(window).on('scroll', onScroll); 
3
4// callback
5function onScroll(){ 
6    if( $(window).scrollTop() + window.innerHeight >= document.body.scrollHeight ) { 
7        track_page++; 
8        load_contents(track_page); 
9    }
10}
11