R Shiny key input binding

Question

In a Shiny application, is it possible to have a binding that listens to what key a user presses down?

I'm not too familiar with JavaScript, but I'm looking for something like:

window.onkeydown = function (e) {
    var code = e.keyCode ? e.keyCode : e.which;
    alert(code);
};

where the key input is then to be used in server.R, e.g.:

shinyServer(function(input, output) {

  output$text <- renderText({
    paste('You have pressed the following key:', input$key)
  })

  # ...

})

Answer 1

You can add a listener for keypresses. The Shiny.onInputChange can be used to bind the key pressed to a shiny variable:

library(shiny)
runApp( list(ui = bootstrapPage(
  verbatimTextOutput("results"),
  tags$script('
    $(document).on("keypress", function (e) {
       Shiny.onInputChange("mydata", e.which);
    });
  ') 
)
, server = function(input, output, session) {

  output$results = renderPrint({
    input$mydata
  })
}
))

for keydown events you can substitute:

  tags$script('
    $(document).on("keydown", function (e) {
       Shiny.onInputChange("mydata", e.which);
    });
  ')