Web Scraping Ajax and Javascript Sites

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2024-05-05 14:00:18

Most crawling frameworks used for scraping cannot be used for Javascript or Ajax. Their scope is limited to those sites that show their main content without using scripting. One would also be tempted to connect a specific crawler to a Javascript engine but it’s not easy to do. You need a fully functional browser with good DOM support because the browser behavior is too complex for a simple connection between a crawler and a Javascript engine to work. There is a list of resources at the end of this article to explore the alternatives in more depth.

Each one of these alternatives has its pros and cons. For example using a complete browser consumes a lot of resources, especially if we need to scrape websites with a lot of pages.

In this post we’ll give a simple example of how to scrape a web site that uses Javascript. We will use the htmlunit library to simulate a browser. Since htmlunit runs on a JVM we will use Jython, an [excellent] programming language,which is a Python implementation in the JVM. The resulting code is very clear and focuses on solving the problem instead of on the aspects of programming languages.

We will scrape the Gartner Magic Quadrant pages at: http://www.gartner.com/it/products/mq/mq_ms.jsp . If you look at the list of documents, the links are Javascript code instead of hyperlinks with http urls. This is may be to reduce crawling, or just to open a popup window. It’s a very convenient page to illustrate the solution.