library(shiny)
runApp(
list(
ui = fluidPage(
tags$script(
"Shiny.addCustomMessageHandler('message', function(params) { alert(params); });"
),
actionButton("btn","Press Me")
),
server = function(input, output, session) {
observeEvent(input$btn,{
randomNumber <- runif(1,0,100)
session$sendCustomMessage("message",list(paste0(randomNumber," is a random number!")))
})
}
)