Javascript 在 Shiny App 中捕获客户点击图像的时间

您可以使用Shiny提供给客户端的javascript函数Shiny.setInputValue.例子:

library(shiny)
ui <- shiny::fluidPage(
                 img(id = 'trigger_image', 
                     src = 'notfound.jpg',
                     height = '100px',
                     width = '100px'
                     ),
                 tags$script('
              document.getElementById("trigger_image").onclick = function(){
              var the_time = new Date().getTime();
              // set input$client_time to the_time:
              Shiny.setInputValue("client_time", the_time)}
        ')
        )

server <- function(input, output) {
    observeEvent(input$client_time,{
        ## do stuff with input$client_time
    })
}

shinyApp(ui, server)

请注意，Javascript getTime返回自1970年1月1日以来经过的毫秒数.

光泽:Communicating with Javascript

Edit

如果必须测量在客户端更新映像和用户响应(单击刷新映像)之间经过的时间，可以在客户端捕获并计算两个事件之间的持续时间，如下所示:

library(shiny)
ui <- shiny::fluidPage(
    tags$script('
    // ------ javascript code ------
    // $(document).ready(...) ensures execution only after document is fully rendered
    // so that events like .onclick can be attached 
    $(document).ready(function(){
        // function to set Shiny input value to current time: 
        const clockEvent = function(inputName){Shiny.setInputValue(inputName, new Date().getTime())}
        // trigger when the value of output id "trigger_image" changes: 
        $(document).on("shiny:value",
               function(event){
                   if (event.target.id === "trigger_image") {clockEvent("displayed_at")}
               }
              )
        // trigger when the image, after being sent or refreshed, is clicked:
        document.getElementById("trigger_image")
                    .onclick = function(){clockEvent("reacted_at")}
    })
    // ------------------------------
    '),
    shiny::imageOutput('trigger_image'),
    actionButton('show_new', 'show new image'),
    textOutput('reaction_time')
)


server <- function(input, output) {
    observeEvent(input$show_new,{
        output$trigger_image <- shiny::renderImage(list(id = 'trigger_image',
                                                        'src' = 'image001.png'
                               ), deleteFile = FALSE)
                               
        output$reaction_time <- renderPrint(paste('reaction time (ms)', input$reacted_at - input$displayed_at))
})
}

shinyApp(ui, server)