A scraper that handles infinite scrolling

scraper.js

const scrapeNumber = 20;
const scrapeQuery = '.userContentWrapper';
const startTime = Date.now();
const lapseTime = 3600000; // that's 1 hour in milliseconds
let arrayOfItems = []; 
let heightBefore = 0;
let heightAfter = 0;

while (arrayOfItems.length < scrapeNumber) {
  await page.evaluate('window.scrollTo(0, document.body.scrollHeight)');
  await page.waitFor(1000);
  arrayOfPostItems = await page.evaluate(() => {
    return [...document.querySelectorAll(scrapeQuery)];
  });
  
  // break loop if scrollHeight is unchanged, signalling the bottom has been reached  
  heightAfter = await page.evaluate('document.body.scrollHeight');
  if (heightBefore === heightAfter) {
    break;
  } else {
    heightBefore = heightAfter;
  }
  
  // break loop if one hour passes
  if (Date.now() - startTime >= lapseTime) {
    break; 
  }
}