wasmbuild

A build tool to generate wasm-bindgen glue code for Deno and the browser.

Setup

Add a task to the deno.json file in your project:

{
  "tasks": {
    "wasmbuild": "deno run -A jsr:@deno/wasmbuild@VERSION_GOES_HERE"
  }
}

Browser, Node.js, or older Deno support

The output is compatible in Deno 2.1+ or Deno 2.1.5+ if published to JSR (due to a bug unfortunately).

Most browsers do not support Wasm imports yet, which this library generates. If you want output that works in more scenarios, build with the --inline flag.

Scaffold project (Optional)

To create a starter Rust crate in an rs_lib subfolder of your project, run:

deno task wasmbuild new

Building

To build, invoke deno task wasmbuild in your project:

deno task wasmbuild

You can now try it out with deno run mod.js

Bindings will be generated at ./lib/<crate-name>.js:

import { add } from "./lib/rs_lib.js";

console.log(add(1, 1));

Checking output is up-to-date

If you're checking your Wasm module into source control, it may occur that someone updates the Rust code, but forgets to build when submitting a PR. To ensure that the output is up-to-date, you can use the --check flag:

deno task wasmbuild --check

For example, in a GitHub action:

- name: Check Wasm up-to-date
  run: deno task wasmbuild --check

CLI flags

• --debug - Build without optimizations.
• --inline - Inline the Wasm module. Useful for scenarios where you want a build output that works in environments that don't support Wasm imports yet.
• --project <crate_name> / -p <crate_name> - Specifies the crate to build when using a Cargo workspace.
• --out <dir_path> - Specifies the output directory. Defaults to ./lib
• --js-ext <ext_no_period> - Extension to use for the wasm-bindgen JS file. Defaults to js.
• --all-features - Build the crate with all features.
• --no-default-features - Build the crate with no default features.
• --features - Specify the features to create. Specify multiple features quoted and with spaces (ex. --features "wasm serialization").
• --skip-opt - Skip running wasm-opt.
• --check - Checks if the output is up-to-date.