title: How to hide a conditional panel in Shiny?
body: <p>How to hide a conditional panel in Shiny? Please, see the following example:</p>
  
  <pre><code>library(shiny)
  
  ui &lt;- fluidPage(
    actionButton("eval","Evaluate"),
    numericInput("num_input", "If number is changed, cp must hide", value = 0),
    conditionalPanel(
        condition = "input.eval",
        "text"))
  
  server &lt;- function(input, output, session) {
    observeEvent(input$num_input, {
      input$eval &lt;- 0
    })}
  
  shinyApp(ui, server)
  </code></pre>
  
  <p>What I want to achieve is: Once the user clicks the evaluate-button the conditional panel should appear, but once the number in <code>num_input</code> is changed the panel should disappear. My idea was to null the evaluate-button, but this does not work (the app opens with gray background and seems frozen).</p>
  
  <p>I also tried it with <code>shinyjs</code> like so:</p>
  
  <pre><code>library(shiny)
  library(shinyjs)
  
  ui &lt;- fluidPage(
    useShinyjs(),
    actionButton("eval","Evaluate"),
    numericInput("num_input", "If number is changed, cp must hide", value = 0),
    conditionalPanel(
        id = "cond_panel",
        condition = "input.eval",
        "text"))
  
  server &lt;- function(input, output, session) {
    observeEvent(input$num_input, {
      reset("cond_panel")})}
  
  shinyApp(ui, server)
  </code></pre>
  
  <p>But this does not work either: the app opens regularly and the conditional panel is shown once the evaluate-button is clicked, but nothing happens once the number is changed.</p>