Web-scraping JavaScript page with Python

Question

We are not getting the correct results because any javascript generated content needs to be rendered on the DOM. When we fetch an HTML page, we fetch the initial, unmodified by javascript, DOM.

Therefore we need to render the javascript content before we crawl the page.

As selenium is already mentioned many times in this thread (and how slow it gets sometimes was mentioned also), I will list two other possible solutions.

Solution 1: This is a very nice tutorial on how to use Scrapy to crawl javascript generated content and we are going to follow just that.

What we will need:

Docker installed in our machine. This is a plus over other solutions until this point, as it utilizes an OS-independent platform.
Install Splash following the instruction listed for our corresponding OS.
Quoting from splash documentation:

Splash is a javascript rendering service. It’s a lightweight web browser with an HTTP API, implemented in Python 3 using Twisted and QT5.

Essentially we are going to use Splash to render Javascript generated content.
Run the splash server: sudo docker run -p 8050:8050 scrapinghub/splash.
Install the scrapy-splash plugin: pip install scrapy-splash
Assuming that we already have a Scrapy project created (if not, let’s make one), we will follow the guide and update the settings.py:
Then go to your scrapy project’s settings.py and set these middlewares:
```
DOWNLOADER_MIDDLEWARES = {
      'scrapy_splash.SplashCookiesMiddleware': 723,
      'scrapy_splash.SplashMiddleware': 725,
      'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware': 810,
}
```
The URL of the Splash server(if you’re using Win or OSX this should be the URL of the docker machine: How to get a Docker container’s IP address from the host?):
```
SPLASH_URL = 'http://localhost:8050'
```
And finally you need to set these values too:
```
DUPEFILTER_CLASS = 'scrapy_splash.SplashAwareDupeFilter'
HTTPCACHE_STORAGE = 'scrapy_splash.SplashAwareFSCacheStorage'
```

Finally, we can use a SplashRequest:

In a normal spider you have Request objects which you can use to open URLs. If the page you want to open contains JS generated data you have to use SplashRequest(or SplashFormRequest) to render the page. Here’s a simple example:
class MySpider(scrapy.Spider):
    name = "jsscraper"
    start_urls = ["http://quotes.toscrape.com/js/"]

    def start_requests(self):
        for url in self.start_urls:
        yield SplashRequest(
            url=url, callback=self.parse, endpoint="render.html"
        )

    def parse(self, response):
        for q in response.css("div.quote"):
        quote = QuoteItem()
        quote["author"] = q.css(".author::text").extract_first()
        quote["quote"] = q.css(".text::text").extract_first()
        yield quote
SplashRequest renders the URL as html and returns the response which you can use in the callback(parse) method.

Solution 2: Let’s call this experimental at the moment (May 2018)…
This solution is for Python’s version 3.6 only (at the moment).

Do you know the requests module (well who doesn’t)?
Now it has a web crawling little sibling: requests-HTML:

This library intends to make parsing HTML (e.g. scraping the web) as simple and intuitive as possible.

Install requests-html: pipenv install requests-html

Make a request to the page’s url:

from requests_html import HTMLSession

session = HTMLSession()
r = session.get(a_page_url)

Render the response to get the Javascript generated bits:
```
r.html.render()
```

Finally, the module seems to offer scraping capabilities.
Alternatively, we can try the well-documented way of using BeautifulSoup with the r.html object we just rendered.

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