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How can you scrape dynamic websites using JavaScript and other client-side technologies?

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Web scraping is the process of extracting data from websites, usually for analysis, automation, or marketing purposes. However, not all websites are easy to scrape, especially those that use dynamic content generated by JavaScript and other client-side technologies. In this article, you will learn how to scrape dynamic websites using JavaScript and other tools, such as headless browsers, web drivers, and frameworks.

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1 What are dynamic websites?

Dynamic websites are websites that change their content based on user interactions, such as clicking, scrolling, or typing. They often use JavaScript, a programming language that runs in the browser, to manipulate the Document Object Model (DOM), which is the structure of the web page. Dynamic websites can provide a better user experience, but they also pose challenges for web scraping, as the content may not be available in the HTML source code or may require specific actions to trigger.

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Vlad Mishkin

Senior Full Stack Engineer (Ruby on Rails, VueJS, AWS)
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Almost any website uses one of JavaScript frameworks nowadays. Such sites can't be scraped with only an HTTP client. A browser and a web driver are needed to render dynamic content correctly.

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2 How to scrape dynamic websites using JavaScript?

One way to scrape dynamic websites using JavaScript is to run your own JavaScript code in the browser, either manually or programmatically. This way, you can access the DOM and extract the data you need. For example, you can use the browser's developer tools to open the console and type commands like document.querySelector("h1").innerText to get the text of the first heading element. Alternatively, you can use tools like Puppeteer or Playwright, which are node.js libraries that allow you to control a headless browser (a browser without a graphical user interface) and execute JavaScript code on any website.

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Ashley Sheridan

Software Engineering Manager at Parkopedia
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One of the drawbacks of scraping dynamic content like this though is that often the dynamic content is often tied to specific events taken by the user. For example, a modal might only be shown when a certain button is clicked, or content might be hidden from the DOM until a particular action is taken.

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3 How to scrape dynamic websites using web drivers?

Another way to scrape dynamic websites using JavaScript is to use web drivers, which are software that communicate with the browser and simulate user actions. Web drivers can automate tasks like clicking, scrolling, typing, and waiting for elements to load. For example, you can use Selenium, a popular web driver that supports various browsers and languages, to create a script that opens a website, fills a form, and submits it. To use Selenium, you need to install a browser-specific driver, such as ChromeDriver or GeckoDriver, and a client library, such as selenium-webdriver for node.js.

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4 How to scrape dynamic websites using frameworks?

A third way to scrape dynamic websites using JavaScript is to use frameworks, which are libraries that provide high-level abstractions and features for web scraping. Frameworks can simplify the process of creating, managing, and running web scraping projects, as well as handling issues like concurrency, caching, logging, and error handling. For example, you can use Scrapy, a popular framework for Python, to create a spider, which is a class that defines how to crawl and extract data from a website. To scrape dynamic websites with Scrapy, you need to install an additional middleware, such as scrapy-splash or scrapy-playwright, that integrates with a headless browser or a web driver.

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5 What are the advantages and disadvantages of scraping dynamic websites using JavaScript?

Scraping dynamic websites using JavaScript has some advantages and disadvantages compared to scraping static websites using HTML parsers. On the one hand, you can access data that is generated or modified by JavaScript, simulate user actions and interactions, and execute your own JavaScript code on the website. On the other hand, you may need to install additional tools, encounter anti-scraping techniques, rate limits, or captchas, and consume more resources. These factors may increase the complexity and overhead of your web scraping project, affect its performance and scalability, and hinder your web scraping activities.

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6 How to improve your web scraping skills and competencies?

Web scraping is a valuable skill for IT professionals, as it can help them collect and analyze data from various sources. To improve your web scraping skills, you should learn the basics of HTML, CSS, and JavaScript. You should also learn how to use tools like browser's developer tools, curl, or Postman to inspect and test websites and requests. Additionally, you should learn how to use libraries and frameworks like Puppeteer, Selenium, or Scrapy to automate and manage web scraping projects. Furthermore, you need to understand how to handle common web scraping challenges such as pagination, authentication, proxies, cookies, headers, or errors. Finally, it’s important to follow web scraping best practices and ethics such as respecting the website's terms of service, robots.txt, and copyright laws.

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7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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Ashley Sheridan

Software Engineering Manager at Parkopedia
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As well as dynamic content scraping, you can use these tools to help aid accessibility testing in a more automated fashion. For example, I've used Puppeteer in the past to check the colour contrast of all text against their background, which will change from element to element.

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How can you scrape dynamic websites using JavaScript and other client-side technologies?

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1 What are dynamic websites?

2 How to scrape dynamic websites using JavaScript?

3 How to scrape dynamic websites using web drivers?

4 How to scrape dynamic websites using frameworks?

5 What are the advantages and disadvantages of scraping dynamic websites using JavaScript?

6 How to improve your web scraping skills and competencies?

7 Here’s what else to consider

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