A little trick for debugging Shiny

This is gonna be a short post about a little trick I’ve been using while developing Shiny Apps. (Spoiler: nothing revolutionary)

A browser anywhere, anytime

The first thing to do is to insert an action button, and a browser() in the < g class="gr_ gr_33 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="33" data-gr-id="33">observeEvent() watching this button. This is a standard approach: at any time, you just press this button, and you’re inside the Shiny Application — then, you can access the value of the < g class="gr_ gr_5 gr-alert gr_spell gr_inline_cards gr_disable_anim_appear ContextualSpelling ins-del multiReplace" id="5" data-gr-id="5">reactiveValues and run the reactive elements, accessing the values they have at the moment you’ve pressed the button.

This approach works, and it’s robust. But here’s the issue: it’s kind of cumbersome to add/remove or comment/uncomment this button when you want to show, make screenshots, or simply remove this button to have a full view of the app.

So here’s a little trick that uses JavaScript to hide the button, and show it using the JavaScript console from your web browser:

# Add to your UI: 
actionButton("browser", "browser"),
tags$script("$('#browser').hide();")
# Add to your server 
observeEvent(input$browser,{
  browser()
})
# And to show the button in your app, go 
# to your web browser, open the JS console, 
# And type:
$('#browser').show();

As said, nothing revolutionary here, just sharing a little trick

Ps: don’t forget to remove this button when you’ll send the app to be deployed to production.

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