selenider and rvest • selenider

selenider can be a useful add-on to rvest, for when scraping data requires interaction with a website.

rvest is very similar to selenider, but is designed for static webpages rather than interactive ones.

library(rvest)
library(selenider)
#> 
#> Attaching package: 'selenider'
#> The following objects are masked from 'package:rvest':
#> 
#>     back, forward

To start, let’s open https://www.r-project.org/

open_url("https://www.r-project.org/")

First, we will interact with the website with selenider. We would like to find the most recent post by R on Mastodon, and follow the link to the original post.

s(".mt-timeline") |>
  find_element("article") |>
  elem_attr("data-location") |>
  open_url()

Now, we would like to parse the text of the post using rvest::html_text2(). We can do this in two ways, either by locating the element containing the post using selenider then parsing it using rvest, or by parsing the entire page using rvest and finding the element after. The two methods are very similar, since selenider and rvest use a very similar syntax, except rvest uses the html_ prefix rather than the elem_ prefix.

We can convert between selenider elements and rvest (or more precisely, xml2) documents using rvest::read_html() or xml2::read_html().

Note that when converting elements to rvest nodes, the element will be wrapped in a <body> tag.

# First method
rvest_element <- s(".columns-area") |>
  find_element(".status__content") |>
  read_html()

rvest_element
#> {html_document}
#> <html>
#> [1] <body><div class="status__content" tabindex="0"><div class="status__conte ...

html_text2(rvest_element)
#> [1] "Registration deadline is this Sunday!\n\nFrom: @R_Contributors\nhttps://hachyderm.io/@R_Contributors/112099342257590328"

Reading the HTML of an entire page can be done using get_page_source(). Note that rvest::html_element() is equivalent to find_element(), but works only on static HTML.

get_page_source() |>
  html_element(".columns-area") |>
  html_element(".status__content") |>
  html_text2()
#> [1] "Registration deadline is this Sunday!\n\nFrom: @R_Contributors\nhttps://hachyderm.io/@R_Contributors/112099342257590328"