CODEWITHSUNDEEP
javascriptnode.jsweb-scrapingpuppeteer
David Daza
David Daza

Reputation: 155

Why am I getting duplicated data when scraping?

I want to learn some web scraping and I found out puppeteer library. I chose puppeteer over other tools because I have some background in JS.

I also found this website whose purpose is to be scraped. I've managed to get the info of every book in every page. Here's what I did:

(async () => {
  const browser = await puppeteer.launch({headless: false});
  const page = await browser.newPage();
  await page.goto(url); // http://books.toscrape.com/

  const json = [];

  let next = await page.$('.pager .next a'); // next button

  while (next) {
    // get all articles
    let articles = await page.$$('.product_pod a');

    // click on each, get data and go back
    for (let index = 0; index < articles.length; index++) {
      await Promise.all([
        page.waitForNavigation(),
        articles[index].click(),
      ]);
      const data = await page.evaluate(getData);
      json.push(data);
      await page.goBack();
      articles = await page.$$('.product_pod a');
    }

    // click the next button
    await Promise.all([
      page.waitForNavigation(),
      page.click('.pager .next a'),
    ]);

    // get the new next button
    next = await page.$('.pager .next a');
  }
  fs.writeFileSync(file, JSON.stringify(json), 'utf8');
  await browser.close();
})();

The function getData passed to page.evaluate returns an object with the desired properties:

function getData() {
  const product = document.querySelector('.product_page');
  return {
    title: product.querySelector('h1').textContent,
    price: product.querySelector('.price_color').textContent,
    description:
      document.querySelector('#product_description ~ p')
        ? document.querySelector('#product_description ~ p').textContent
        : '',
    category:
      document.querySelector('.breadcrumb li:nth-child(3) a')
        ? document.querySelector('.breadcrumb li:nth-child(3) a').textContent
        : '',
    cover:
      location.origin +
      document.querySelector('#product_gallery img')
          .getAttribute('src').slice(5),
  };
}

When I finally execute the script, everything goes well except that in the final json file I have duplicated records. This is, every book has two entries within the file. I know that the script could be better but what do you think is happening with this approach?

Upvotes: 0

Views: 495

Answers (1)

QHarr
QHarr

Reputation: 84465

Your selector in this line:

let articles = await page.$$('.product_pod a');

is matching more than is required. You get 40 not 20 ( a child tags for image container are also included which are the same as the child a of h3)

You want to restrict to the h3 a:

let articles = await page.$$('.product_pod h3 a');

Upvotes: 2

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