I Don’t Need No Stinking API: Web Scraping For Fun and Profit

I can see site operators being against the practice though, as it (usually): - generates no ad revenue - often enables someone else to use data that you struggled to put together, allowing others to profit with no gain for you - hit's edge cases that were never optimized for (as it does not follow real user access)

In the past, I have successfully used HtmlUnit to fulfill my admittedly limited scraping needs.

It runs headless, but it has a virtual head designed to pretend it's a user visting a web application to be be tested for QA purposes. You just program it to go through the motions of a human visting a site to be tested (or scraped). E.g., click here, get some response. For each whatever in the response, click and aggregate the results in your output (to whatever granularity).

Alas, it's in Java. But, if you use JRuby, you can avoid most of the nastiness that implies. (You do need to know Java, but at least you don't have to write Java.)

Hartley, what is your recommended toolkit?

I note you mentioned the problem of dynamically generated content. You develop your plan of attack using the browser plus Chrome Inspector or Firebug. So far, so good. But what if you want to be headless? Then you need something that will generate a DOM as if presenting a real user interface but instead simply returns a reference to the DOM tree that you are free to scan and react to.

The article does slide into the sketchy side (I've always wanted an excuse to do that client side javascript trick too) but I found it more interesting because of that, these aren't secrets. Maybe if I put my "won't somebody please think of the children" hat on I agree that glorifying using trojan code to potentially ddos someones server to get around rate limits desired by the owners of the server is bad. Adults and especially adult self described hackers should be able to read this without mock outrage, it's interesting and it's happening all the time.

You can't condemn web scraping though, that's the backbone of the services we all depend on for most internet related things. That's the whole point of structured markup and the world wide web itself.

I do know that Selenium can be used for this...but am yet to see a decent example for the same. Does anyone have any good resources/examples on JS scraping that they could share?? I would be eternally grateful.

I've been doing this on a site that is 100% Javascript-driven for over a year, very successfully.

It's really no different than hitting a static site with Selenium. Figuring out the proper XPath to use is often the biggest challenge: Chrome Developer tools help immensely. Also, you need to watch for delays in JS rendering, so put a lot of pauses in your scripts.

It's of course slow, so if you want to distribute it across several machines, use Selenium Grid or a queue system (SQS, Resque, etc). Setup Xvfb to run on headless Linux instances.