Setting a Loading Message for a DataTable in RMarkdown

Thomas Williams wants you to wait patiently:

Waits are inevitable, whether getting data from an API or database, or manipulating data in an interactive R Markdown document. Showing a “loading” or “updating” message is a beneficial incremental improvement to users’ experience.

The code at https://github.com/thomasswilliams/r-markdown-snippets/blob/main/loading-message-datatable.Rmd, when run from RStudio, demonstrates using CSS and pseudo-elements to display text in a DataTables (DT package).

Read on to see an example of how to use this.