Simple script for implementing endless scroll

endless-scroll.js

var offset = 4;

$(window).scroll(function() {
  if($(window).scrollTop() + $(window).height() > ($(document).height() - 150)) {
    loadMore(offset);
    offset = offset + 4;
  }
});

function loadMore(offset) {
  $.ajax({
    url: '/load_more',
    data: { offset: offset },
    async: false,
    cache: false,
    timeout: 30000,
    success: function (result) {
      $('.product-grid').append(result);
    }
  });
}