r - r中shinyjs中的For循环有什么问题？

Question

我不知道如何使用 Shinyjs 库在 Shiny R 应用程序中的 javascript 中使 For 循环工作。如果我在脚本中添加任何 For 循环，工作脚本将停止运行。

演示该问题的最小示例代码如下。取消注释 For 循环（删除/*和*/行）会使代码不起作用。

请看一看。谢谢你。

library(shiny)
library(shinyjs)

ui <- fluidPage(
  # pressing this button increments counter
  actionButton("button", "press"),
  # text showing counter value
  textOutput("text"),
  # place to store the javascript
  uiOutput("default"),
  useShinyjs()
)

server <- function(input, output, session) {
  counter <- 1
  output$default <- renderUI({
    # this script sends current value of the counter back to Shiny as input$result
    # For loop is dot doing anything
    # if For loop is inside comment - the script works
    # if the loop is not commented - the script does not work
    tags$script("
                Shiny.addCustomMessageHandler('bttn_pressed', function(value) {
                  var i;
                  /*
                  for (i = 0; i < 2; i++) {
                  }
                  */
                  Shiny.setInputValue('result', value, {priority: 'event'});
                });"
    )
  })
  
  # update text output with the value reported by javascript
  observeEvent(input$result, {
    output$text <- renderText({input$result})
  })
  
  # increment the counter and send the updated value to javascript
  observeEvent(input$button, {
    counter <<- counter + 1
    session$sendCustomMessage("bttn_pressed", counter)
  })
}

shinyApp(ui = ui, server = server)

标签： rshinyshinyjs