Shiny: Disable Button

server.R

library(shiny)

disableActionButton <- function(id,session) {
  session$sendCustomMessage(type="jsCode",
                             list(code= paste("$('#",id,"').prop('disabled',true)"
                                    ,sep="")))
}

shinyServer(function(input, output,session) {
  
  observe({
    if(input$btn1 == 0) return()
    disableActionButton("btn2",session)
  })
})

ui.R

library(shiny)


shinyUI(basicPage(
  tags$head(tags$script(HTML('
      Shiny.addCustomMessageHandler("jsCode",
        function(message) {
          console.log(message)
          eval(message.code);
        }
      );
    ')))
  ,actionButton("btn1","Disable the other button")  
  ,actionButton("btn2","Button")
)
)