Run The Code From npm

This portion of the tutorial will help you create a Webpack JavaScript project that will run your WebAssembly code in the browser.

Scaffold a JavaScript Project

To scaffold a project that we can use our new package in, we'll use an npm template called create-wasm-app. To use this run this command in a directory different than your Rust project:

npm init wasm-app

This tool will ask you for the name of a project, and then create a directory with that name.

If we look in that directory, we'll see the following:

  • .gitignore: ignores node_modules
  • LICENSE-APACHE and LICENSE-MIT: most Rust projects are licensed this way, so these are included for you
  • README.md: the file you are reading now!
  • index.html: a bare bones html document that includes the webpack bundle
  • index.js: example js file with a comment showing how to import and use a wasm pkg
  • package.json and package-lock.json:
  • webpack.config.js: configuration file for bundling your js with webpack

Add Your npm Package

The scaffolded project includes an example WebAssembly package, hello-wasm-pack, in your package.json. Go into the package.json file, add your package, and remove the hello-wasm-pack dependency from the "dependencies" section.

Now, open up the index.js file. Replace the hello-wasm-pack in the first line with the name of your package:

import * as wasm from "<your package name>";

wasm.greet();

Run The Project

Before we run our project, we need to make sure we install our dependencies:

npm install

We should be ready to run our project now! To run our project we'll run:

npm start

Then in a web browser navigate to http://localhost:8080 and you should be greeted with an alert box that says "Hello World!".

If you did congrats you've successfully uploaded your first bit of wasm code to npm and used it properly!