I want to change the placeholder in fileInput after a file has been uploaded, i.e. customize the "No file selected" to any string I choose.

I found how to customize the progress bar label, so I'm guessing the code should be quite similar. This is what I tried so far:
library(shiny)
library(shinyjs)
jscode_upload_msg <- " Shiny.addCustomMessageHandler('upload_msg', function(msg) {
var target = $('#fileUpload_progress').children()[0];
target.innerHTML = msg;
}); "
jscode_upload_txt <- " Shiny.addCustomMessageHandler('upload_txt', function(txt) {
var target = $('#fileUpload_header').children()[1].children()[0];
target.innerHTML = txt;
}); "
ui <- fluidPage(
useShinyjs(),
tags$script(jscode_upload_msg),
tags$script(jscode_upload_txt),
fileInput("fileUpload", "File to upload")
)
server <- function(input, output, session ) {
observe({
req(input$fileUpload)
session$sendCustomMessage("upload_msg", "YOUR TEXT")
session$sendCustomMessage("upload_txt", "SOME OTHER TEXT")
})
}
shinyApp(ui = ui, server = server)
From https://stackoverflow.com/questions/49506469/shiny-customise-fileinput, it seems that the input field is in the second position. However, I am not sure how to write the jscode. Any advice?