TL;DR: This package works with Splash rendering servers which are really just a REST API & `lua` scripting interface to a QT browser. It's an alternative to the Selenium ecosystem which was really engineered for application testing & validation.
Sometimes, all you need is a page scrape after javascript has been allowed to roam wild and free over meticulously crafted HTML tags. So, this package does not do _everything_ Selenium can in pure R (though, the Lua interface is equally as powerful and accessible via R), but if you're just trying to get a page back that needs javascript rendering, this is a nice, lightweight, consistent alternative.
It's also an alternative to the somewhat abandoned `phantomjs` (which you can use in R within or without a Selenium context as it's it's own webdriver) and it may be useful to compare renderings between this package & `phantomjs`.
The package uses the [`stevedore`](https://github.com/richfitz/stevedore) package to orchestrate Docker on your system (if you have Docker and more on how to use the `stevedore` integration below) but you can also do get it running in Docker on the command-line with two commands:
when done. All of that happens on your localhost and you will not need to specify `splash_obj` to many of the `splashr` functions if you're running Splash in this default configuration as long as you use named parameters. You can also use the pre-defined `splash_local` object if you want to use positional parameters.
Now, you can run Selenium in Docker, so this is not unique to Splash. But, a Docker context makes it so that you don't have to run or maintain icky Python stuff directly on your system. Leave it in the abandoned warehouse district where it belongs.
>'Splash' <https://github.com/scrapinghub/splash> is a javascript rendering service. It’s a lightweight web browser with an 'HTTP' API, implemented in Python using 'Twisted'and 'QT' [and provides some of the core functionality of the 'RSelenium' or 'seleniumPipes' R packages but with a Java-free footprint]. The (twisted) 'QT' reactor is used to make the sever fully asynchronous allowing to take advantage of 'webkit' concurrency via QT main loop. Some of Splash features include the ability to process multiple webpages in parallel; retrieving HTML results and/or take screenshots; disabling images or use Adblock Plus rules to make rendering faster; executing custom JavaScript in page context; getting detailed rendering info in HAR format.
Mini-DSL (domain-specific language). These can be used to create a "script" without actually scripting in Lua. They are a less-powerful/configurable set of calls than what you can make with a full Lua function but the idea is to have it take care of very common but simple use-cases, like waiting a period of time before capturing a HAR/HTML/PNG image of a site:
- `splash_press`: Trigger mouse press event in web page.
- `splash_release`: Trigger mouse release event in web page.
- `splash_send_keys`: Send keyboard events to page context.
- `splash_send_text`: Send text as input to page context, literally, character by character.
- `splash_user_agent`: Overwrite the User-Agent header for all further requests. NOTE: There are many "helper" user agent strings to go with `splash_user_agent`. Look for objects in `splashr` starting with `ua_`.
- <strike>_Possibly_ writing R function wrappers to install/start/stop Splash</strike> which would also support enabling javascript profiles, request filters and proxy profiles from with R directly, using [`harbor`](https://github.com/wch/harbor)
NOTE: ALL of these examples assume Splash is running in the default configuraiton on `localhost` (i.e. started with `start_splash()` or the docker example commands) unless otherwise noted.
You can use [`HARtools::HARviewer`](https://github.com/johndharrison/HARtools/blob/master/R/HARviewer.R) — which this pkg import/exports — to get view the HAR in an interactive HTML widget.
Please note that this project is released with a [Contributor Code of Conduct](CONDUCT.md). By participating in this project you agree to abide by its terms.
