react log.r

?showReactLog

options(shiny.reactlog=TRUE); 

session$sendCustomMessage(type="jsCode",
  						  list(code= paste("$('#",id,"').prop('disabled',true)"
							  				 ,sep="")))

  tags$head(tags$script(HTML('
      Shiny.addCustomMessageHandler("jsCode",
        function(message) {
          console.log(message)
          eval(message.code);
        }
      );

sessionclose.r

shinyServer(function(input, output, session) {
  session$onSessionEnded(function() {
    # The session ended
  })
})

 session$isClosed() method.