Communication between R and javascript works on laptop but not after deployment

Hello, I am making a shiny app.R which is communicating to a javascript file using session$sendCustomMessage in R and Shiny.addCustomMessageHandler in javascript file. The way I do so is by starting a local server in the folder where my javascript file resides using web server for chrome. I copy paste the server URL in R shiny like tags$script(src = "") where myscript.js is the javascript file and the server runs in the www folder where I keep the file. On my computer the app is working perfectly fine.

However, when I deploy my app on shinyapps, I deleted the server URL that is used to access file because the URL was a local server on my laptop. I expected that since the javascript file is in www, shinyapps should automatically be able to access it. As soon as I click the action button in my app that is supposed to activate the .js code, the browser says "Disconnected from the server". I am assuming this might be because shinyapps can not acces the .js code? Is there a way where I can put my js code on some kind of server that can provide a URL like how it did when I made a local server on Chrome? Any help will be greatly appreciated. Thank you!

I have provided the relevant R shiny code below. Here is the app:
If you click on the "state" tab, select any state and click the green check mark, the app will disconnect. I have also attached screenshot of the local Chrome server I make, in case that helps

ui <- fluidPage(id = "page", theme = "styles.css",
    tags$head(tags$link(rel = "stylesheet", type = "text/css", href = "styles.css")),
    tags$body(HTML('<link rel="icon", href="favicon.png",
                       type="image/png" />')), # add logo in the tab
    tags$div(class = "header",
             tags$img(src = "iow_logo.png", width = 75),
             tags$h1("US Water Budget App"),
             titlePanel(title="", windowTitle = "IoW Water Budget App")),
    navbarPage(title = "",
               selected = "Home",
               theme = "styles.css",
               fluid = TRUE,
      tabPanel(title = "Home"),
      tabPanel(title = "State",
        column(width = 12,
          column(width = 3,
                 selectInput(inputId = "states",
                             label = "Select state",
                             choices = state_choices)), #defined above UI
          column(width = 2, 
               actionButton(inputId = "runButton", 
                            label = "",
                            icon = icon("check"))
        tags$body(tags$div(id = "container")),
        tags$script(src = "d3.js"), 
        tags$script(src = "myscript.js")
    tabPanel(title = "Exact Match"),
    tabPanel(title = "Sub-Component"),
    tabPanel(title = "Partial Sub-Component"),
    navbarMenu(title = "About",
               tabPanel(title = "Other stuff"))

server <- function(input, output, session){
  observeEvent(input$runButton, {
    if (input$states != "All states") {
      selection_df <- df %>%
        filter(jL %in% input$states) %>%
      selection_df <- select(selection_df, -jL)
      selection_json <- d3_nest(data = selection_df, root = input$states)
    else {
      selection_df <- df
      selection_json <- d3_nest(data = selection_df, root = "States")
    leaf_nodes <- nrow(selection_df)
    session$sendCustomMessage(type = "canvas_height", leaf_nodes)
    session$sendCustomMessage(type = "nested_json", selection_json)

I solved this. If you provide script src to the java script file in tags$head(), you don't need web server for chrome. And it works fine :slight_smile: