Shiny Cookie Based Authentication Example, please visit https://calligross.de/post/using-cookie-based-authentication-with-shiny/ for more information.

app.R

library(shiny)
library(shinyjs)

if (!dir.exists('www/')) {
  dir.create('www')
}

download.file(
  url = 'https://cdn.jsdelivr.net/npm/js-cookie@2/src/js.cookie.min.js',
  destfile = 'www/js.cookie.js'
)

addResourcePath("js", "www")

# This would usually come from your user database. But we want to keep it simple.
password_hash <- bcrypt::hashpw('secret123') # Never store passwords as clear text
sessionid <- "OQGYIrpOvV3KnOpBSPgOhqGxz2dE5A9IpKhP6Dy2kd7xIQhLjwYzskn9mIhRAVHo" # Our not so random sessionid


jsCode <- '
  shinyjs.getcookie = function(params) {
    var cookie = Cookies.get("id");
    if (typeof cookie !== "undefined") {
      Shiny.onInputChange("jscookie", cookie);
    } else {
      var cookie = "";
      Shiny.onInputChange("jscookie", cookie);
    }
  }

  shinyjs.setcookie = function(params) {
    Cookies.set("id", escape(params), { expires: 0.5 });  
    Shiny.onInputChange("jscookie", params);
  }

  shinyjs.rmcookie = function(params) {
    Cookies.remove("id");
    Shiny.onInputChange("jscookie", "");
  }
'

server <- function(input, output) {

  status <- reactiveVal(value = NULL)
  # check if a cookie is present and matching our super random sessionid  
  observe({
    js$getcookie()
    if (!is.null(input$jscookie) && input$jscookie == sessionid) {
        status(paste0('in with sessionid ', input$jscookie))
    }
    else {
      status('out')
    }
  })

  observeEvent(input$login, {
    if (input$username == 'admin' & bcrypt::checkpw(input$password, hash = password_hash)) {
      # generate a sessionid and store it in your database, but we keep it simple in this example...
      # sessionid <- paste(collapse = '', sample(x = c(letters, LETTERS, 0:9), size = 64, replace = TRUE))
      js$setcookie(sessionid)
    } else {
      status('out, cause you don\'t know the password secret123 for user admin.')
    }
  })
  
  observeEvent(input$logout, {
    status('out')
    js$rmcookie()
  })
  
  output$output <- renderText({
    paste0('You are logged ', status())}
  )
}

ui <- fluidPage(
  tags$head(
    # you must copy https://raw.githubusercontent.com/js-cookie/js-cookie/master/src/js.cookie.js to www/
    tags$script(src = "js/js.cookie.js")
  ),
  useShinyjs(),
  extendShinyjs(text = jsCode),
  sidebarLayout(
    sidebarPanel(
      textInput('username', 'User', placeholder = 'admin'),
      passwordInput('password', 'Password', placeholder = 'secret123'),
      actionButton('login', 'Login'),
      actionButton('logout', 'Logout')
    ),
    mainPanel(
      verbatimTextOutput('output')
    )
  )
)

shinyApp(ui = ui, server = server)

Error: shinyjs: extendShinyjs: functions argument must be provided.

got it: extendShinyjs(text = jsCode, functions=c("getcookie","setcookie","rmcookie"))