Print any JavaScript console.log messages in the R console

When developing and debugging a Shiny that uses custom JavaScript code, it can be helpful to use console.log() messages in JavaScript. This function allows you to see these messages printed in the R console directly rather than having to open the JavaScript console in the browser to view the messages.

This function must be called in a Shiny app's server.

showLog()

Note

Log messages that cannot be serialized in JavaScript (such as many JavaScript Event objects that are cyclic) will not be printed in R.

See also

logjs()

Examples

if (interactive()) {
  library(shiny)

  shinyApp(
    ui = fluidPage(
      useShinyjs(),
      textInput("text", "Type something")
    ),
    server = function(input, output) {
      showLog()
      logjs("App started")
      observe({
        logjs(paste("Length of text:", nchar(input$text)))
      })
    }
  )
}