从服务器端更改selectinput的边框颜色

Question

This is a followup question to this question. In the previous question the border of selectInput was changed from the ui side using the following argument tags$head(tags$style(HTML( "#Select1 ~ .selectize-control.single .selectize-input {border: 1px solid #dd4b39;}"))) . Now I would like to change the border colour of a particular select output from the server side. My main aim is actually to change the colour based of different conditions. To change the colour from the server side I tried the following code but it does not seem to work. Is there a way to achieve this?

Here is the code I tried:

library(shiny)

  ui <- fluidPage(

    tags$head(tags$style(htmlOutput("Border_Arg"))),

    selectInput("Select1", "Option1", choices = NULL),

    selectInput("Select2", "Option2", choices = NULL)
  )


  server <- function(input, output){
    output$Border_Arg <- renderUI({"#Select1 ~ .selectize-control.single .selectize-input {border: 1px solid #dd4b39;}"})
  }

  shinyApp(ui = ui, server = server)

Answer 1

You were close.

Find a running example below:

library(shiny)
ui <- fluidPage(
  selectInput("Select1", "Option1", choices = NULL),
  selectInput("Select2", "Option2", choices = NULL),
  uiOutput("Border_Arg")
)


server <- function(input, output){
  output$Border_Arg <- renderUI({
    tags$head(tags$style(HTML( "#Select1 ~ .selectize-control.single .selectize-input {border: 1px solid #dd4b39;}")))
  })
}

shinyApp(ui = ui, server = server)