How do I handle download progress monitoring in Puppeteer?
Ava W

To extract data from a paginated table using Puppeteer, you need to automate the pagination process to load and extract data from multiple pages. Here's a detailed explanation: 1. Launching a new browser instance and creating a new page:

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   const puppeteer = require('puppeteer');

   (async () => {
     const browser = await puppeteer.launch();
     const page = await browser.newPage();

     // Perform actions with the page here

     // Close the browser
     await browser.close();
   })();

This code sets up a basic Puppeteer script. It launches a new headless browser instance and creates a new page to work with. 2. Extracting data from a paginated table: To extract data from a paginated table, you need to follow these steps: - Identify the table element and the pagination controls: Identify the table element that contains the data you want to extract, as well as the pagination controls that allow you to navigate between pages. - Extract data from the current page: Use Puppeteer's DOM manipulation methods or evaluate JavaScript code within the page's context usingpage.$$eval() orpage.evaluate() to extract data from the table on the current page. - Navigate to the next page: Interact with the pagination controls to navigate to the next page. This may involve clicking on a "next" button or directly changing the page number in the pagination control. - Repeat the process until all pages have been processed: Continue extracting data and navigating to the next page until you have processed all the pages in the pagination.

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   async function extractDataFromPaginatedTable() {
     const tableSelector = '#tableId';
     const nextPageSelector = '.nextPageButton';

     let currentPage = 1;
     let extractedData = [];

     while (true) {
       const dataOnPage = await page.$$eval(tableSelector + ' tr', (rows) => {
         return Array.from(rows, (row) => {
           const columns = row.querySelectorAll('td');
           return Array.from(columns, (column) => column.textContent.trim());
         });
       });

       extractedData = extractedData.concat(dataOnPage);

       const nextPageButton = await page.$(nextPageSelector);

       if (!nextPageButton) {
         // No more pages to load, exit the loop
         break;
       }

       // Click the next page button to navigate to the next page
       await nextPageButton.click();
       await page.waitForNavigation();

       currentPage++;
     }

     console.log('Extracted data:', extractedData);
   }

   await extractDataFromPaginatedTable();

In this example, theextractDataFromPaginatedTable() function is defined to handle the extraction of data from a paginated table. It usespage.$$eval() to extract data from the table on each page and appends the extracted data to an array. It also interacts with the pagination controls to navigate to the next page usingpage.$() andpage.waitForNavigation(). The function repeats this process until there are no more pages to process. By utilizing this approach, you can extract data from a paginated table using Puppeteer. This allows you to automate the extraction of data from multiple pages of the table and collect the complete dataset for further processing or analysis. Regarding handling download progress monitoring in Puppeteer, it does not provide direct methods to monitor download progress. Puppeteer focuses more on browser automation and data extraction from web pages. However, you can indirectly monitor download progress by intercepting the network requests and monitoring the progress of specific requests. Here's an overview of the process: 1. Intercepting network requests: Use Puppeteer'spage.setRequestInterception(true) method to enable request interception. 2. Listening torequest events: Set up an event listener for therequest event to intercept and handle network requests. 3. Tracking download progress: Inside the event listener, you can track the progress of specific requests by accessing therequest.headers['content-length'] andresponse.headers['content-length'] values. You can calculate the progress as a percentage based on the difference between the bytes received and the total content length. 4. Handling the download completion: Once the download is complete, you can perform any necessary actions, such as saving the downloaded file or processing its content. Here's an example to illustrate the process:

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const puppeteer = require('puppeteer');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();

  await page.setRequestInterception(true);

  page.on('request', (request) => {
    if (request.url().endsWith('.pdf')) {
      const downloadRequest = request;

      downloadRequest.on('response', (response) => {
        const totalBytes = parseInt(response.headers['content-length'], 10);
        let receivedBytes = 0;

        response.on('data', (data) => {
          receivedBytes += data.length;
          const progress = (receivedBytes / totalBytes) * 100;

          console.log(`Download Progress: ${progress.toFixed(2)}%`);
        });

        response.on('end', () => {
          console.log('Download Complete');
          // Perform further actions with the downloaded file
        });
      });
    }

    request.continue();
  });

  await page.goto('https://example.com/download');

  await browser.close();
})();

In this example, the code sets up a Puppeteer script that intercepts network requests and specifically tracks the progress of a PDF download. Once the download request is identified, the script calculates the progress based on the bytes received and the total content length. When the download is complete, it logs a completion message and can proceed with further actions on the downloaded file. Please note that this approach may not work for all types of downloads or file formats. It heavily relies on the server providing theContent-Length header for accurate progress tracking. Additionally, the example focuses on tracking progress for a specific file type (PDF in this case), but you can modify it to suit your specific download requirements.

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