How to use shiny javascript functions with modules? - r

Question

I want to include some javascript in my shiny module, but regardles of what I tried the javascript is not appear in the final app. What am I doing wrong?
App.r:
library(shiny)
source("examplemod.R")
ui <- fluidPage(
tags$head(
tags$script(src="shinyjavascript.js")
),
sidebarLayout(
sidebarPanel(
examplemodUI("example")
),
mainPanel(
)
)
)
server <- function(input, output) {
callModule(examplemod, "example")
}
shinyApp(ui, server)
Module:
examplemodUI<-function(id){
ns <- NS(id)
tagList(
textOutput(ns("prb"))
)
}
examplemod<- function(input, output, session) {
output$prb<-renderPrint({
input$one
})
}
shinyjavascript.js
$( document ).on("shiny:sessioninitialized", function(event) {
Shiny.onInputChange("one", "noone");
});

Answer 1

First, check that your shinyjavascript.js can be found by the browser. Run your add and open it in a browser. Chrome has a better inspector module than RStudio's built in app viewer (the one that pops up when you run an app). In the browser's Inspector, find the reference to shinyjavascript.js both in the "Elements" pane and that the contents can be loaded in the "Sources" pane.
If it's there, but cannot be loaded, ensure that the file is placed in a subdirectory www from where your app's R source files are located.
If the file is found and loaded, update it to the following for some good ol' fashioned debugging:
console.log('JavaScript file loaded')
$( document ).on("shiny:sessioninitialized", function(event) {
console.log('session initialized')
Shiny.onInputChange("one", "noone");
});
Reload the page and look for these two lines in the console. This will give us a hint to how far your code runs.
Update:
Once satisfied your javascript is loaded and running, we move on to the next. Does your app receive the value and why doesn't it update?
output$prb<-renderPrint is a reactive that only executes if and only if Shiny as prb binded to an output control. This could be your case, or it's that input$one doesn't work. So, we separate the two.
Try to update the following:
server <- function(input, output) {
callModule(examplemod, "example")
observe({cat(input$one, '\n')})
}
This should print 'noone' to the R console.
If that works, move the new observe line to your module:
examplemod<- function(input, output, session) {
output$prb<-renderPrint({
input$one
})
observe({cat(input$one, '\n')})
}
and see if you get a response there.
Update 2 with solution:
So, I've detailed how I would debug these problems. But have found a solution. It requires 3 small changes:
examplemod<- function(input, output, session, one) { # 1
output$prb<-renderPrint({
one() # 2
})
callModule(examplemod, "example", reactive(input$one)) # 3
But I cannot offer any explanation as to why you cannot use input directly...