library(shiny)

randomNumberButton <- function(inputID){
    tagList(
        singleton(
            tags$head(tags$script(src="button.js"),
                      tags$script(src="button-binding.js"))
        ),
        tags$div(
            id = inputID,
            tags$button(
                type = "button",
                class = "random-number-generator",
                "Click"
            )
        )
    )
}

ui <- fluidPage(
    # random number generator
    randomNumberButton("test"),
    textOutput("printTest")
)

server <- function(input, output, session) {
    observeEvent(input$test,{
        output$printTest <- renderText(input$test)
    })
}

shinyApp(ui, server)