How to get screen resolution from JavaScript in R Shiny? - Stack Overflow

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I want to get screen resolution from JavaScript, stored in the GetScreenWidth variable on Shiny Server.

I tried the reference:

1. Receiving data from .js in server.R shiny
2. /

So I have:

ui.R

shinyUI(
  bootstrapPage(

    verbatimTextOutput("results")
    ,tags$script('
        var jsWidth = screen.width;
        Shiny.onInputChange("GetScreenWidth",jsWidth);
    ')
   )
 )

server.R

 shinyServer(function(input,output){

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

 })

It will return NULL by verbatimTextOutput.

How should I modify the code? Thanks!

I want to get screen resolution from JavaScript, stored in the GetScreenWidth variable on Shiny Server.

I tried the reference:

1. Receiving data from .js in server.R shiny
2. https://ryouready.wordpress./2013/11/20/sending-data-from-client-to-server-and-back-using-shiny/

So I have:

ui.R

shinyUI(
  bootstrapPage(

    verbatimTextOutput("results")
    ,tags$script('
        var jsWidth = screen.width;
        Shiny.onInputChange("GetScreenWidth",jsWidth);
    ')
   )
 )

server.R

 shinyServer(function(input,output){

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

 })

It will return NULL by verbatimTextOutput.

How should I modify the code? Thanks!

• javascript
• r
• shiny
• screen
• resolution

Share Improve this question Follow edited Jul 21, 2017 at 13:29 Badacadabra 8,52777 gold badges3131 silver badges5454 bronze badges asked Oct 21, 2015 at 2:42 Robin ChenRobin Chen 10333 bronze badges

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1 Answer 1

Sorted by: Reset to default 11

The problem is that you're running the JavaScript code before Shiny is initialized. You can use the new feature that tells you when shiny is ready, here's example code

jscode <-
'$(document).on("shiny:connected", function(e) {
  var jsWidth = screen.width;
  Shiny.onInputChange("GetScreenWidth",jsWidth);
});
'

library(shiny)
runApp(shinyApp(
  ui = fluidPage(
    tags$script(jscode)
  ),
  server = function(input, output, session) {
    observe({
      cat(input$GetScreenWidth)
    })
  }
))

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