Building local packages for WebR

We’ve recently added WebR support for extendr.

Tip

WebR is a distribution of the R programming language that runs natively in WebAssembly. WebAssembly is binary format that runs directly in the browser.

Using WebR means that R can be used directly by the browser / JavaScript without a backend server running R for you.

Typically, folks rely on R-universe to build their packages for WebR. However, compiled packages require a bit more work. Figuring out how to build a package for WebR locally was surprsingly confusing and also very straightfoward.

I’ve releaned how to do this a few times now. Here is how it is done:

How to build for WebR

The easiest way to build a local package for WebR is using the Docker image.

To do so, cd into your R package you want to build. Then spin up the Docker image and then enter R from inside of the container.

docker run -it --rm -v ${PWD}/output:/output -w /output ghcr.io/r-wasm/webr:main
R

Then from R inside of the container, run rwasm::build(".").

That’s it!

Thanks to George Stagg for helping with this!