This post is the sixth one of a series of post about webR:

• Using webR in an Express JS REST API
• The Old Faithful Geyser Data shiny app with webR, Bootstrap & ExpressJS
• Preloading your R packages in webR in an Express JS API
• Using my own R functions in webR in an Express JS API, and thoughts on building web apps with Node & webR
• Rethinking webR package & functions preloading with webR 0.2.2
• A starter pack for building NodeJS projects with webR inside

Note: the first post of this series explaining roughly what webR is, I won’t introduce it again here.

Again, a new project?

Most of the previous posts have been about poking around with webR inside NodeJS, but nothing stable on how to build an app.

That’s something I’m trying to change. Based on the experience gathered building apps in R (in {shiny} with {golem}) and in JavaScript, I’ve tried to come up with a solution for a starter kit for building what I think will be the perfect skeleton for webR/NodeJS project.

The idea is to have one project with inside:

• One R package
• One JS app
• A tool that brings the R package into the NodeJS app and allow to use the R functions inside JavaScript

This skeleton needed a toolkit to perform the following task:

1️⃣ From a cli point of view:

• init the project with a specific skeleton
• allow to install packages from the webr CRAN to a local webr library, in the spirit of previous post.
• allow to install the deps from a DESCRIPTION file

2️⃣ From a NodeJS point of view:

• Load the packages downloaded in a local webr library
• Create an interface to load and manipulate the functions from a package downloaded from CRAN, and use them in JS.
• Same but with a local package folder

For the function manipulation mechanism, I wanted something that would allow to think in terms of pkg::fun() but in JavaScript, which would translate as pkg.fun() in your Node app. Something I had implemented in another old NodeJS module called hordes, which I can now safely deprecate in favor of the following tools.

The reasoning being: the R dev writes a standalone package that exports an xyz function, then the web team can load this package, and launch xyz() without writing any R code.

webrcli & spidyr

So, here comes webrcli and spidyr.

❗️ Please note that these tools are work in progress and has been used very few times and only for example apps, will need a lot of bug fixes and documentation, so if ever you plan on using it be indulgent, and report any bug or feature request ❗️

Project init

These packages are made to be used together, and here is an example of how to use them:

# Global installing webrcli
npm install -g webrcli
# Init a webrcli project
cd /tmp
webrcli init webrspongebob

👉 Initializing project ----
(This may take some time, please be patient)
👉 Copying template ----
👉 Installing {pkgload} ----
✅ {pkgload} downloaded and extracted ----

✅ {cli} downloaded and extracted ----

✅ {crayon} downloaded and extracted ----

✅ {desc} downloaded and extracted ----

✅ {fs} downloaded and extracted ----

✅ {glue} downloaded and extracted ----

✅ {pkgbuild} downloaded and extracted ----

✅ {rlang} downloaded and extracted ----

✅ {rprojroot} downloaded and extracted ----

✅ {withr} downloaded and extracted ----

✅ {R6} downloaded and extracted ----

✅ {callr} downloaded and extracted ----

✅ {processx} downloaded and extracted ----

✅ {ps} downloaded and extracted ----

The project is now created, let’s move into it.

cd ./webrspongebob
tree -L 1

.
├── index.js
├── node_modules
├── package-lock.json
├── package.json
├── rfuns
└── webr_packages

4 directories, 3 files

Here is how it’s organized:

• index.js is the main file for the app, node_modules the standard folder for the node deps
• package-lock.json / package.json are standard Node metadata files
• rfuns contains the R package that will be added to the NodeJS app
• webr_packages contains the R dependencies

We can launch the app with node index.js and it will output:

node index.js
👉 Loading WebR ----
👉 Loading R packages ----
ℹ Loading rfuns
[ 'Hello, world!' ]
✅ Everything is ready

Let’s dive a bit inside the index.js:

const path = require('path');
const { WebR } = require('webr');
const { loadPackages, LibraryFromLocalFolder } = require('spidyr');

const rfuns = new LibraryFromLocalFolder("rfuns");


(async () => {

  console.log("👉 Loading WebR ----");
  globalThis.webR = new WebR();
  await globalThis.webR.init();

  console.log("👉 Loading R packages ----");

  await loadPackages(
    globalThis.webR,
    path.join(__dirname, 'webr_packages')
  )

  await rfuns.mountAndLoad(
    globalThis.webR,
    path.join(__dirname, 'rfuns')
  );

  const hw = await rfuns.hello_world()

  console.log(hw.values);

  console.log("✅ Everything is ready!");

})();

Here are the bits that are specific to a spidyr project:

const rfuns = new LibraryFromLocalFolder("rfuns");

This function will take a local folder containing an R package, and load the functions from this package into the rfuns object. Here, for example, our R package contains one R function, hello_world(), it will then be available in NodeJS as rfuns.hello_world() once the mountAndLoad function is called.

await loadPackages(
  globalThis.webR,
  path.join(__dirname, 'webr_packages')
)

await rfuns.mountAndLoad(
  globalThis.webR,
  path.join(__dirname, 'rfuns')
);

The first bit loads the webr_packages folder, containing all the R dependencies, then the second bit mount the local folder into the webR file system and load the functions.

Finally, const hw = await rfuns.hello_world() calls the function from the R package, and its value is console.loged just after that.

With a CRAN package

And now, how do I load a CRAN package? For example, let’s say I want to use {spongebob} in my app?

First, let’s install {spongebob} via webrcli :

webrcli install spongebob

✅ {spongebob} downloaded and extracted ----

Then, let’s update our index.js:

const path = require('path');
const { WebR } = require('webr');
const { loadPackages, LibraryFromLocalFolder, Library } = require('spidyr');

const rfuns = new LibraryFromLocalFolder("rfuns");
const spongebob = new Library("spongebob");

(async () => {

  console.log("👉 Loading WebR ----");
  globalThis.webR = new WebR();
  await globalThis.webR.init();

  console.log("👉 Loading R packages ----");

  await loadPackages(
    globalThis.webR,
    path.join(__dirname, 'webr_packages')
  )

  await rfuns.mountAndLoad(
    globalThis.webR,
    path.join(__dirname, 'rfuns')
  );

  await spongebob.load(
    globalThis.webR
  );

  const hw = await rfuns.hello_world()

  console.log(hw.values);

  const said = await spongebob.tospongebob("hello from spongebob")

  console.log(said.values)

  console.log("✅ Everything is ready!");;

})();

Here:

• const spongebob = new Library("spongebob"); will create a lib, ready to mount a package
• await spongebob.load(globalThis.webR) will load all the functions from the {spongebob} package
• const said = await spongebob.tospongebob("hello from spongebob") will run the spongebob::tospongebob() R function

Then :

node index.js

👉 Loading WebR ----
👉 Loading R packages ----
ℹ Loading rfuns
[ 'Hello, world!' ]
[ 'helLo fROm spONgEbOb' ]
✅ Everything is ready!

Some random notes

The webrspongebob example is available at https://github.com/ColinFay/webrspongebob

About the current implementation

• Right now I’m not really sure how this handles the infix function like %>% for example. That being said, this might not be a function you’d want to use in the current way of building things.

• The exported functions are read via getNamespaceExports("pkg") and getExportedValue("pkg", "fun"), if ever this is not the perfect way to do this in base R but I’ll be happy to find some other ways to do this.

• webrcli and spidyr both encapsulate code run in webR, especially webrcli which has an R script which is sourced and run in a webR instance.

Future

Please do try these tools. I would be very happy to have your feedback on the philosophy, and on the general workflow.

If ever you find a bug or have an idea, feel free to open issues.