R shiny - Animated random numbers to ValueBox - r

Question

I want to make a little animation in R shiny.
The core is to put a sample(1:100, 1), in a valueBox, but I'd like to make an animation by printing random numbers for some seconds and and in the end print the sample result.
I've found the following code, which uses JavaScript. The problem is that the code generates an animation from 0 to the random number generated in sample.
library(shiny)
library(shinydashboard)
js <- "
Shiny.addCustomMessageHandler('anim',
function(x){
var $box = $('#' + x.id + ' div.small-box');
var value = x.value;
var $icon = $box.find('i.fa');
var $s = $box.find('div.inner h3');
var o = {value: 0};
$.Animation( o, {
value: value
}, {
duration: 1000
}).progress(function(e) {
$s.text((e.tweens[0].now).toFixed(0));
});
}
);"
# UI
ui <- dashboardPage(
skin = "black",
dashboardHeader(title = "Test"),
dashboardSidebar(disable = TRUE),
dashboardBody(
tags$head(tags$script(HTML(js))),
fluidRow(
tagAppendAttributes(
valueBox("", subtitle = "Número sorteado",
icon = icon("server"),
color = "blue"
),
id = "mybox"
)
),
br(),
actionButton("btn", "Change value")
)
)
# Server response
server <- function(input, output, session) {
rv <- reactiveVal()
observeEvent(input[["btn"]], {
rv(sample(1:100, 1))
})
observeEvent(rv(), {
for(i in 1:30){
session$sendCustomMessage("anim", list(id = "mybox", value = rv()))
}
})
}
shinyApp(ui, server)
I've also found this code that makes exactly what I want in JS, but I couldn't put it in shiny.

Answer 1

There's no need to resort to Javascript. Shiny has a built-in timer.
This MWE creates a value box displaying an integer chosen at random in the range 1 to 100 that updates once a second.
library(shiny)
library(shinydashboard)
ui <- dashboardPage(
dashboardHeader(),
dashboardSidebar(),
dashboardBody(
valueBoxOutput("random")
)
)
server <- function(input, output, session) {
output$random <- renderValueBox({
invalidateLater(1000, session)
valueBox("Value", sample(1:100, 1))
})
}
shinyApp(ui = ui, server = server)