How to send user input HTML to R function

I've some shiny app with button ("btn"), when I click on it I get shintalert:

observeEvent(input[["btn"]], {
    shinyalert(
      title = "some title",
      type = "info",
      showConfirmButton = FALSE,   
      html = TRUE,
      text = div(HTML(
             "<form>                                                 
             <textarea id='my_txt' name='my_txt' rows='8' cols='100'></textarea>
             <input type='text' id='my_txt2' name='my_txt2'  style='display: block;'/>
             <button onclick= ",SOME_R_FUNCTION(my_txt,my_txt2 ),">click me</button>
             </form>"
             ))
             )})
     

In the form I've 2 text boxes and one button. When the user click on the button I want to send the user input of both text-boxes to my R function - SOME_R_FUNCTION. I cant find how I can do it.

library(shiny)
library(shinyalert)

ui <- basicPage(
  useShinyalert(),
  actionButton("btn", "Click me")
)

server <- function(input, output){
  observeEvent(input[["btn"]], {
    shinyalert(
      title = "some title",
      type = "info",
      showConfirmButton = FALSE,   
      html = TRUE,
      text = "<div>
          <textarea id='my_txt' name='my_txt' rows='8' cols='100'></textarea>
          <input type='text' id='my_txt2' name='my_txt2' style='display: block;'/>
          <button>click me</button>
        </div>",
      callbackJS = "function(){Shiny.setInputValue('userInputs', [$('#my_txt').val(), $('#my_txt2').val()]);}"
    )
  })
  
  observeEvent(input[["userInputs"]], {
    # apply your R function here
    print(input[["userInputs"]])
  })
  
}

shinyApp(ui, server)