Blogpost: https://blog.apify.com/how-to-never-miss-a-beat-on-ever-changing-websites-8cccfa25f5cb

page-function.js

function pageFunction(context) {
  var $ = context.jQuery
  var posts = $('.athing').toArray(); // All posts as array of DOM elements
  var $moreLink = $('.morelink');     // Link to next page
  
  // If crawler is scraping 2nd, 3rd, ... page then 
  // context.request.referrer.pageFunctionResult contains 
  // result from previous pages.
  var prevResult = context.request.referrer 
    ? context.request.referrer.pageFunctionResult 
    : {};
  
  if ($moreLink.length) {
    // Enqueue next page to be crawled.
    context.enqueuePage({ url: $moreLink.prop('href') });
    
    // If there is link to another page then we don't want to output
    // result of this page in order to merge it with the next one
    context.skipOutput();
  }
  
  // Scrape the data and merge them with previous results.
  return posts.reduce(function (result, el) {
    var $el = $(el);
    var link = $el.find('.storylink').attr('href');
    var rank = 101 - parseInt($el.find('.rank').text());

    result[link] = rank;
    
    return result;
  }, prevResult);
}