docs/guide/javascript.md

In devOpifex/leprechaun: Create Simple 'Shiny' Applications as Packages

JavaScript

To include JavaScript in the application you can technically just place .js files within the inst/assets directory.

However, a more robust way is probably to use packer, it allows building R project with webpack to minify JavaScript, scope CSS, and much more, visit the official website for more information.

Example

Create a package and scaffold a leprechaun application from within it.

usethis::create_package("myapp")
leprechaun::scaffold()

Once this done you can use scaffold (almost) any of the scaffolds that packer provides, though there is a scaffold dedicated to leprechaun.

packer::scaffold_leprechaun()

── Scaffolding leprechaun ─────────────────────────────────────────────────── 
✔ Initialiased npm
✔ webpack, webpack-cli, webpack-merge installed with scope "dev…
✔ Added npm scripts
✔ Created srcjs directory
✔ Created srcjs/config directory
✔ Created webpack config files

── Adding files to .gitignore and .Rbuildignore ──

✔ Setting active project to '/home/jp/Projects/test'
✔ Adding '^srcjs$' to '.Rbuildignore'
✔ Adding '^node_modules$' to '.Rbuildignore'
✔ Adding '^package\\.json$' to '.Rbuildignore'
✔ Adding '^package-lock\\.json$' to '.Rbuildignore'
✔ Adding '^webpack\\.dev\\.js$' to '.Rbuildignore'
✔ Adding '^webpack\\.prod\\.js$' to '.Rbuildignore'
✔ Adding '^webpack\\.common\\.js$' to '.Rbuildignore'
✔ Adding 'node_modules' to '.gitignore'

── Scaffold built ──

ℹ Run `bundle` to build the JavaScript files
ℹ Run `leprechaun::use_packer()`

One of the last messages reminds us to run the use_ function for packer, let's go ahead and do that.

leprechaun::use_packer()

The packer scaffold created, amongst other files, a srcjs directory where the JavaScript code lives.

The basic template includes a simple handler for the show-packer message, it expects a text variable as part of the message. This message is then simply displayed in an alert.

If we modify the server function to use send_message to send text to the show-packer message handler.

server <- function(input, output, session){
    send_message <- make_send_message(session)  

    send_message("show-packer", text = "Hello leprechaun!")
}

This will make it such that loading the application will send the message to the front-end and display the alert.

But first, we need to bundle the JavaScript, thanks to the packer feature this can be done with the leprechaun::build function.

leprechaun::build()

You can then generate the documentation, load the package and run the app.

devtools::document()
devtools::load_all()
run()

devOpifex/leprechaun documentation built on April 17, 2025, 4:31 a.m.