Hiding dashboardHeader issues on shiny server :collapsed = TRUE does not work on shiny server

shinydashboard

#1

collapsed = TRUE does not work on shiny server. but it work on local R.

I use the same code. but on shiny server does not collapse.

shiny server:

local R:

###########  in app.R   ###################  
###########  ui  ###################  
library(shiny)
library(shinydashboard)
ui=function(request) { 
  dashboardPage(
    dashboardHeader(title = "Basic dashboard"),
    dashboardSidebar(collapsed = TRUE),
    dashboardBody(
      # Boxes need to be put in a row (or column)
      fluidRow(
        box(
          title = "Controls",
          sliderInput("slider", "Number of observations:", 1, 100, 50)
        )
        ,box(plotOutput("plot1", height = 250)
        )
      )
    ))
}

######   server ###############################
server=function(input, output) {
  set.seed(122)
  histdata <- rnorm(500)

  output$plot1 <- renderPlot({
    data <- histdata[seq_len(input$slider)]
    hist(data)
  })
}

shinyApp(ui = ui, server = server)