Shinyalert:我如何知道用户是按了OK还是Cancel？

library(shiny)
library(shinyalert)

ui <- fluidPage(
  useShinyalert(),
  
  actionButton("show_alert", "显示警报框")
)

server <- function(input, output, session) {
  observeEvent(input$show_alert, {
    shinyalert(
      title = "警报框",
      text = "您确定要执行此操作吗？",
      type = "warning",
      showCancelButton = TRUE,
      closeOnClickOutside = FALSE,
      callbackR = TRUE,
      callback = jsCallback
    )
  })
  
  jsCallback <- '
    function (isConfirm) {
      if (isConfirm) {
        // 用户按下了OK按钮
        Shiny.setInputValue("user_choice", "OK");
      } else {
        // 用户按下了Cancel按钮
        Shiny.setInputValue("user_choice", "Cancel");
      }
    }
  '
  
  observeEvent(input$user_choice, {
    choice <- input$user_choice
    
    if (choice == "OK") {
      # 用户按下了OK按钮，执行相应的操作
      # ...
    } else if (choice == "Cancel") {
      # 用户按下了Cancel按钮，采取适当的措施
      # ...
    }
  })
}

shinyApp(ui, server)