library(leaflet)
library(shiny)

# set basic ui
ui <- fluidPage(
  leafletOutput("map")
)

server <- shinyServer(function(input, output) {

  # produce the basic leaflet map with single marker
  output$map <- renderLeaflet(
    leaflet() %>%
      addProviderTiles("CartoDB.Positron") %>%
      addCircleMarkers(lat = 54.406486, lng = -2.925284)

  )

  # observe the marker click info and print to console when it is changed.
  observeEvent(input$map_marker_click,
               print(input$map_marker_click)
               )

})


shinyApp(ui, server)