Improve performance by vectorisation

[mgirlich]

Creating HTML tags and marking text as HTML is pretty slow because it isn't vectorised. It would be great to have vectorised interface for such situations. This would help to improve the performance of rendering big tables with {gt}.
In rstudio/gt#1470 I improved the performance of rendering a gt table. There are some more optimisations to be done but now about a quarter of the time is spent in htmltools::tag() and htmltools::HTML().

Overall, I think improving the performance of creating HTML and the rendering would be a great help for gt (and other packages that need to render a bit more HTML).

[B-Nilson]

Seconding this - when trying to create thousands of shiny tags performance is relatively poor without vectorization. Especially if you want HTML/character as the output type, not shiny.tag (like if building custom popups for a leaflet map)

For example:

test = data.frame(text = rep("test", 3000), id = 1:3000)

# Using paste() (vectorized, but messy)
system.time(paste("<span id='", test$id, "'>", test$text, "</span>") |> 
  htmltools::HTML())
# user  system elapsed 
# 0       0       0 

# Using tags (not vectorized, but cleaner code)
system.time(lapply(1:nrow(test), \(i) 
  htmltools::span(id = test$id[i], test$text[i]) |> 
    as.character() |> htmltools::HTML()))
# user  system elapsed 
# 0.36    0.00    0.81